Biostatistics Multiple Choice Questions
Leitzmann et al. examined the link between drinking coffee and gallstone disease. Individuals who drank between 2 and 4 cups of coffee per day had a relative risk of developing symptomatic gallstones of 0.6. How should the results be interpreted? a) 1 b) 3 c) 1, 2 d) 2, 3 e) 1, 2, 3 1. Individuals who drink coffee were more likely to develop gallstone 0.6 times when compared with those who do not. 2. Individuals who drink coffee were more likely to develop gallstone 40% lower than those who do not. 3. Individuals who drink coffee were more likely to develop gallstone 60% greater than those who do not.
2, 3
Which of the following is TRUE with respect to the term "random chance?" a) Outcomes of clinical trials may be affected by random chance b) Statistical tests help to determine the effect of random chance on the study outcomes c) Random chance is also known as "systematic variation" d) A and B e) All of the above
A and B
Which of the following would INCREASE the amount of Type II error in a study? a) Reduction in sample size b) Reducing the size of delta (assuming sample size remained constant) c) Lack of randomization d) A and B e) All of the above
A and B
A trial is likely to be underpowered, biased, or misleading if which of the following occurred? a) A large number of participants are lost to follow-up. b) A substantial number of participants do not adhere to the study intervention. c) Baseline variables are not balanced between intervention groups. d) All of the above
A large number of participants are lost to follow-up.
Which of the answer sets below best matches the definitions in the left column with the stages of testing new therapies listed in the right column? a) A, C, E, D, B b) C, A, B, D, E c) E, A, B, D, C d) A, B, E, D, C __ Studies involving animals or cell cultures __ Conducted to determine the safety of a treatment in humans. Patients go through intense monitoring __ Large studies (may or may not be a randomized trial) conducted after the therapy has been approved by the FDA to assess the rate of serious side effects and explore further therapeutic uses __ Relatively large randomized blinded trials used to evaluate the efficacy of an intervention __ Investigator explores test tolerability, safe dosage, side effects, and how the body copes with the drug Preclinical A. Phase I B. Phase II C. Phase III D. Phase IV
A, B, E, D, C
The researcher wants to investigate blood cholesterol levels in patients who follow a diet either low or moderate in fat and who take either a drug to lower cholesterol or a placebo. What is the most appropriate statistical test to use in analyzing the data? Independent t-test a) ANOVA b) Chi-square test c) Mann-Whitney U test d) Wilcoxon signed rank test
ANOVA
You are evaluating a randomized, double-blind, parallel-group, controlled trial that compares four antihypertensive drugs for their effect on BP. The authors conclude that hydrochlorothiazide is better than atenolol (p<0.05) and that enalapril is better than hydrochlorothiazide (p<0.01), but no difference is observed between any other drugs. The authors used independent t-test to test the hypothesis that each drug was equal to the other. Which of the following statements is TRUE? a) The authors used the appropriate statistical test to analyze their data b) Enalapril is the most effective of these drugs c) ANOVA would have been a more appropriate test d) A paired t-test is a more appropriate test e) None of the above
ANOVA would have been a more appropriate tes
Researchers designed a study looking at cardiovascular deaths comparing a new drug to placebo. They determined that they would need 200 patients in each group to detect a 15% difference in cardiovascular endpoints given 90% power and a significance level of 0.01. Which of the following changes would require the researchers to increase their sample size? a) Aim to detect a difference of 20% Specify a power of 80% b) Use a significance level of 0.05 c) Aim to detect a difference of 10% d) None of the above
Aim to detect a difference of 10%
A study is internally valid if: a) A repeated-measures design was used b) A causal relationship is confirmed c) An experimental design was used d) All alternative explanations of the results can be ruled out e) It can be generalized to the population
All alternative explanations of the results can be ruled out
Which of the following is a TRUE statement? a) Statistical significance does not assure that the results are clinically significant b) If the p values are small (i.e., less than alpha), then clinical significance should always be interpreted c) If the p values are large (i.e., greater than alpha), then clinical significance should NOT be evaluated d) A and C e) All of the Above
All of the Above
When p-values are not statistically significant, the following conclusions can be reached. a) The amount of Type II error should be evaluated b) The p-value is greater than the significance level c) The test might not have had enough power to produce a statistically significant result d) All of the above
All of the above
Which of the following statements about intention-to-treat (ITT) method of data analysis is true? ITT: a) Analysis the data from all patients enrolled in the trial according to their original treatment b) Provides the best estimate of the efficacy of an intervention for patient who are adherent to the treatment c) Reduces the statistical power of a study compared with the use of a per-protocol analysis d) Decreases the generalizability of the results compared to the use of a per-protocol analysis
Analysis the data from all patients enrolled in the trial according to their original treatment
Patients may alter their behavior when they know they are being observed under study conditions. Which of the following terms best describes this phenomenon? a) Contamination bias b) Selection bias c) Volunteer bias d) Attention bias (Hawthorne effect) e) Admission rate bias (Berkson's paradox)
Attention bias (Hawthorne effect)
One of the main limitations of a cross-over design in drug studies in humans is: a) The study is conducted during a specified time "window" b) Requires a washout period to remove any residual effects from previous drug treatments c) If a drug induces a permanent effect (i.e. antibiotic cure), cross-over designs cannot be used d) B and C e) All of the above
B and C
Which of the following best describes the function of the inclusion criteria for a study? a) Ensures patient safety b) Describes the characteristics of the sample c) Is important in evaluating the external validity of the study d) B and C e) None of the above
B and C
A case-control study was conducted in Kenya to test for the effectiveness of insecticide bed nets as a way to reduce malaria. People who developed Malaria were matched against those who did not and whether or not they slept with bednets was recorded. Results are given in the table below. The investigators use the Chi-square test to see if there is an association between use of bednets and the contraction of malaria. If we fail to reject the null hypothesis a) We could have made a Type II error b) We conclude there is an association between use of bednets and malaria c) Our test has not shown an association between malaria and use of bednets d) Both (a) and (c)
Both (a) and (c)
Eighty-seven patients with bronchoalveolar cancer, a rare condition were compared to 286 non cancer patients and 297 patients with other types of cancer, matched by age, sex and race. They were interviewed about their history of cigarette smoking. A strong relationship was observed between smoking and alveolar cancer (Morabia and Wynder 1992). The disadvantages of the study are: a) There may be recall bias concerning smoking history b) Choice of control group may affect results c) Since the disease is rare it will be difficult to get enough cases that will get the disease d) Both A and B
Both A and B
Case-control study is being conducted to assess the association between first MI and calcium channel blocker use in patients with hypertension. Which of the groups had a statistically significant increase in the odds of MI? Diuretics OR = 1 Beta-blockers OR = 1.09 (0.74-1.63) Beta-blockers + diuretics OR = 0.97 (0.62-1.52) CCB OR = 1.58 (1.04-2.39) CCB + diruestics = 1.70 (0.97-2.99) a) Diuretics b) Beta-blockers c) Calcium channel blockers d) Calcium channel blockers in combination with diuretics
Calcium channel blockers
Eighty-seven patients with bronchoalveolar cancer, a rare condition were compared to 286 non cancer patients and 297 patients with other types of cancer, matched by age, sex and race. They were interviewed about their history of cigarette smoking. A strong relationship was observed between smoking and alveolar cancer (Morabia and Wynder 1992). This is an example of a: a) Case control study b) Cohort study c) Cross-sectional study
Case control study
To determine if fasting is associated with dengue fever, data from 60 patients with dengue fever were collected. These patients were matched for age, sex, and race to 40 patients without dengue fever. The hospital charts of these patients were then reviewed to determine whether they also fasted prior to their illness. What is the type of study design? a) Cross-sectional study b) Prospective cohort study c) Case-control study d) Retrospective cohort study e) Randomized clinical trial
Case-control study
A study is conducted retrospectively and collects data on patients who developed a myocardial infarction (MI) and gathers data on another set of patients who haven't had a MI. Differences in exposures to Drug A are compared between the groups, and an odds ratio is calculated. This type of research design is known as: a) Cross-sectional b) Case report c) Cohort study d) Case/control study e) None of the above
Case/control study
A study tests whether the use of a new drug adherence aid has an effect on CHF exacerbations. Researchers want to evaluate the proportion of patients with an exacerbation of their CHF symptoms in a group of people who used the adherence aid compared with a group of people who did not. To assess whether the changes observed are statistically significant, which one of the following tests is best? a) McNemar b) Chi-square c) Independent t-test d) Mann-whitney U-test e) None of the above
Chi-square
A study is conducted prospectively to determine the effects of Drug A versus Drug B in preventing myocardial infarctions (MIs). One hundred patients in each group were treated with either Drug A or Drug B, and the following results were obtained over a 10 year period: Drug A = 7% of patients had an MI Drug B = 10% of patients had an MI What would be the appropriate inferential statistical test that would be used to compare the percentage of patients experiencing a myocardial infarction associated with Drug A versus Drug B? a) Chi-square analysis b) One-way ANOVA c) Independent student t-test d) None of the above
Chi-square analysis
In a clinical trial, 60 people received a new drug and 50 people received a placebo. Of the people on the new drug, 40 of the 60 showed a positive response and 25 of the 50 people on placebo showed a positive response. What is the most appropriate statistical test to use in determining if the new drug shows more of an effect than the placebo? a) Chi-square analysis b) Mann Whitney U test c) Independent student t-test d) None of the above
Chi-square analysis
Researchers evaluated the percentage of patients who achieved less than a target BP (<140/90 mmHg) when initiate on two different doses of amlodipine. In the study of 200 patients, the amlodipine 5-mg group (n=100) versus the amlodipine 10-mg group (n=100) were compared. The researchers used the percentage of patients who achieve the target goal at 6 months as their primary outcome. Which is the best statistical test to answer the research question? a) Independent t-test b) Wilcoxon signed rank test c) Chi-square or Fisher's exact d) Wilcoxon rank sum e) None of the above
Chi-square or Fisher's exact
The independent variable is marital status (single/married/separated or divorced). The dependent variable is whether or not the person had been hospitalized in the preceding 12 months. The most appropriate statistical test is a(n): a) T-test b) ANOVA c) Chi-square test d) Mann-Whitney U test e) Paired t-test
Chi-square test
Leitzmann et al. examined the link between drinking coffee and gallstone disease. Individuals who drank between 2 and 4 cups of coffee per day had a relative risk of developing symptomatic gallstones of 0.6. What type of study was this? a) Case report b) Cross-sectional study c) Case control study d) Clinical trial e) Cohort study
Cohort study
A study is conducted to determine the effect of Vitamin C tablets on mortality. After the study is completed, the data indicate that patients taking Vitamin C tablets had a decrease in mortality. However, the study design did not control for the effects of dietary Vitamin C. Which of the following terms best describes the role of DIETARY Vitamin C in this study? a) Independent variable b) Dependent variable c) Confounding variable d) Control variable e) None of the above
Confounding variable
Suppose a researcher is interested in assessing the adequacy of an instrument to measure the theoretical conceptualization of "Quality of Pharmaceutical Care". The type of validation procedure would most probably be: a) Content b) Concurrent c) Construct d) Face e) Predictive
Construct
A study wishes to assess birth characteristics in a population. Which of the following variables describes the appropriate measurement scale? -Birthweight in grams
Continuous
Subjects serve as their own controls in which of the following research design? a) Factorial Design b) Parallel Design c) Cross-over Design d) Randomized Control Trial e) Case-control study
Cross-over Design
In a randomized trial of patients who received a cadaver renal transplant, 100 were treated with cyclosporine and 50 were treated with conventional immunosuppression therapy. The difference in treatment was not statistically significant at the 5% level. Therefore: a) This study has proven that cyclosporine is not effective b) Cyclosporin could be significant at the 1% level c) Cyclosporin could be significant at the 10% level d) The groups have been shown to be the same e) The treatment should not be compared because of the differences in the sample sizes.
Cyclosporin could be significant at the 10% level
An analgesic medication was compared to an identical appearing placebo by random assignment to separate treatment groups. Pain was measured on a scale where 0 = none, 1 = mild, 2 = moderate and 3 = severe. Pain was measured at baseline to determine if the two groups were similar. Before the data were collected, the investigators stated that the level of pain 8 hours after a single dose of analgesic was the primary end point. Nevertheless, they measured pain every hour after the dose for 8 hours. To evaluate the statistical analysis, you first need to identify the level of measurement for the study variables. Which of the following is correct? a) IV is an ordinal level of measurement b) DV is a nominal level of measurement c) DV is an ordinal level of measurement d) DV is an interval level of measurement
DV is an ordinal level of measurement
A study comparing two statins finds a mean LDL of 152 mg/dl in the lovastatin group and 165 ml/dl in the newstatin group (p=0.09). How should these results be interpreted? a) Depends on the study power b) Both are equally effective c) Lovastatin and newstatin can be used interchangeably d) Setting the p-value at <0.10 would be more useful
Depends on the study power
You are on the advisory board of a pharmaceutical company that has developed a new drug for stroke prevention in AF. The company decided to conduct a non-inferiority trial to compare the new anticoagulant (Drug A) with warfarin (standard treatment). Which one of the following best describes what you and the researchers set out to prove the alternative hypothesis? a) Drug A is better than warfarin by a factor of delta b) Drug A is worse than warfarin by a factor of delta c) Drug A is not worse than warfarin by a factor of delta d) Drug A is the same as warfarin
Drug A is not worse than warfarin by a factor of delta
When the researcher simultaneously manipulates two independent variables, the design is a: a) Randomized control trial b) Factorial design c) Cross-over design d) Repeated measures design e) Cohort study
Factorial design
The use of inferential statistics permits the researcher to: a) Generalize to a population based on information gathered from a sample b) Interpret descriptive statistics c) Describe information obtained from empirical observation d) Repeat the null hypothesis Select a level of significance
Generalize to a population based on information gathered from a sample
A study is currently designed to detect a 15% difference in response rates between two treatments for breast cancer with a p<0.05. If the investigators wish to be able to detect a 10% difference, which of the following changes do they need to make? a) Decrease the sample size b) Increase the sample size c) Select an level of 0.01 as the cutoff for statistical significance d) Select an level of 0.001 as the cutoff for statistical significance
Increase the sample size
What would be the appropriate inferential statistical test that would be used to compare hemoglobin A1C between two groups, one receiving standard diabetes care and the other cared for by a pharmacist diabetes educator? a) Independent t-test b) Wilcoxon signed rank test c) Paired t-test d) Chi-squared test e) None of the above
Independent t-test
If you decided to reject the null hypothesis when it was false you a) Made a correct decision b) Made both a type I and type II error c) Made a type I error d) Made a type II error
Made a correct decision
An analgesic medication was compared to an identical appearing placebo by random assignment to separate treatment groups. Pain was measured on a scale where 0 = none, 1 = mild, 2 = moderate and 3 = severe. Pain was measured at baseline to determine if the two groups were similar. Before the data were collected, the investigators stated that the level of pain 8 hours after a single dose of analgesic was the primary end point. Nevertheless, they measured pain every hour after the dose for 8 hours. The next step in the evaluation of the statistical analysis is to select a test that is appropriate for the levels of measurement and a test that tests the primary hypothesis. You must also decide if a test for repeated measures is warranted. Which of the following statistical tests would be most appropriate to test the primary hypothesis stated in Case D? a) Fisher's exact test b) Wilcoxon signed-rank test c) Mann-whitney U test d) Student's t-test for independent groups
Mann-whitney U test
Two different creams are used to treat athlete's foot. Each subject with this infection on both feet is given a treatment of Hilocream on one foot while their other foot is treated with Fungacream. The results are shown below. What is the most appropriate statistical test to use in determining if there is a difference between the two treatments? a) McNemars' test b) Mann-Whitney U test c) Paired t-test d) Wilcoxon Signed-rank test
McNemars' test
A study is conducted to determine the effects of 2 drugs on blood pressure reduction (measured in mmHg). When plotted out on a frequency distribution, the data are NOT normally distributed. Which of the following measures of central tendency would be most appropriate to use for these data? a) Mean b) Median c) Mode d) A and B e) None of the above
Median
An analgesic medication was compared to an identical appearing placebo by random assignment to separate treatment groups. Pain was measured on a scale where 0 = none, 1 = mild, 2 = moderate and 3 = severe. Pain was measured at baseline to determine if the two groups were similar. Before the data were collected, the investigators stated that the level of pain 8 hours after a single dose of analgesic was the primary end point. Nevertheless, they measured pain every hour after the dose for 8 hours. Now that you know the level of measurement, which descriptive statistics would be most appropriate to summarize the pain in each group at each time point? a) 95% confidence interval for the median b) Mean and standard error of the mean c) Mean and standard deviation d) Median and interquartile range
Median and interquartile range
Patients are recruited into a clinical trial. The main dependent variable is to determine the average change in cholesterol level between 2 different medications in a randomized, parallel, prospective, double-blinded trial for the average person living in America. An advertisement is placed on the wall of a local fitness center, and patients from the fitness center respond to the advertisement. Based on this information, which is the most likely bias to affect this study? a) Publication bias b) Therapeutic personality bias c) Selection bias d) Membership bias
Membership bias
A study was conducted to evaluate an antibiotic in the treatment of possible bacteremia. Five hundred children with fever but no focal infection were randomly assigned to the antibiotic or to a placebo. All patients were re-evaluated after 48 hours. The authors reported the proportion of children with major infectious morbidity among those with bacteremia was 13% in the placebo group and 10% in the antibiotic group. The 95% confidence interval for the difference in proportions was -2.6% to +8.6%. Thus, the most important conclusion is that: a) The difference in major infection morbidity between placebo and antibiotic is statistically significant b) The proportion of children with major infection morbidity is the same with placebo and antibiotic c) No statistically significance exists in the proportions of children that received placebo and antibiotic. d) The study has low power to detect a difference owing to the small sample size, and no conclusion should be drawn until a larger study is done e) Using a chi-square test to determine significance is preferable to determining a confidence interval for the difference
No statistically significance exists in the proportions of children that received placebo and antibiotic.
A study wishes to assess birth characteristics in a population. Which of the following variables describes the appropriate measurement scale? -Type of delivery classified as cesarean, natural, induced
Nominal
A study wishes to assess birth characteristics in a population. Which of the following variables describes the appropriate measurement scale? -Type of delivery classified as alive and dead
Nominal, Dichotomous, Binary
CASE B. The following 3 questions are based on CASE B A study is developed to compare the efficacy in lowering diastolic blood pressure (DBP) between 2 different antihypertensives. The authors provide the following information: Alpha < 0.05 Beta = 0.2 Power = 80% Delta = 5 mm Hg (also known as the expected effects size) Sigma = 10 mm Hg N = 120 patients/group The study results indicate that on average, Drug A can reduce BP by 20 mm Hg, and Drug B can reduce BP by 8 mm Hg. The p value for this comparison is p = 0.01. NOTE: Assume that a reasonable clinical difference in blood pressure reduction is 5 mm Hg between groups and that the population variance is expected to be 10 mm Hg. Which of the following is a TRUE statement (based on data from CASE B)? a) The results are statistically insignificant b) The result is clinically insignificant. c) Statistical power should be evaluated in order to determine the chance of a Type II error d) The Null Hypothesis would be accepted, based on the p value e) None of the above
None of the above
CASE D. The following 3 questions are based on CASE D A study comparing the efficacy of two H2 blockers in the treatment of patients with duodenal ulcers was conducted. The study determined that Drug A had a 90% cure rate, and that Drug B had an 84% cure rate. The following information is supplied: (Curediff) = 6% (Curediff = Drug A - Drug B = 90% - 84%) (95%CIdiff) = +2%, +10% (95%CIdiff = 95% confidence interval for the difference in ulcer cure rates) What is the correct interpretation of the 95% confidence interval for the difference in ulcer cure rates? a) We are 95% confident that the difference in ulcer cure rates for the sample lies within the interval +2, +10 b) We are 95% confident that the difference in ulcer cure rates for the sample lies within the interval between 84% and 90% c) We are 95% confident that the difference in ulcer cure rates for the population lies within the interval between 84% and 90% d) B and C e) None of the above
None of the above
In clinical trials, which of the following statements is TRUE? a) The acceptable amount of Type I error is usually > 5% The acceptable amount of Type II error is usually > 20% b) Statistical power will increase as the size of delta decreases (assuming the sample size remains constant) c) A and B d) None of the above
None of the above
A study is conducted to determine the efficacy of 2 drugs in preventing seasickness. Measurements are taken to assess the following: no seasickness, mild seasickness, or severe seasickness. Which of the following data types best describes these measurements? a) Nominal b) Ordinal c) Interval d) Ratio e) Integer
Ordinal
A study wishes to assess birth characteristics in a population. Which of the following variables describes the appropriate measurement scale? -Birthweight classified as low, medium, high
Ordinal
You are performing a pharmacokinetic study in which you plan to measure Cmax and AUC of a new drug alone and in combination with a CYP450 enzyme inhibitor in a crossover design. What is the best statistical test for these parameters? a) Wilcoxon signed rank test b) Chi-squared test c) Student's t-test d) Paired student's t-test
Paired student's t-test
An analysis was conducted to determine the impact of drug therapy on blood pressure (measured in mmHg) using a crossover design. Drug A was given to all patients in the first period and measurements were taken, a washout occurred, and then Drug B was given to the same patients and measurements were again taken. What would be the appropriate statistical test to determine whether the mean blood pressures after taking Drug A were different from the mean blood pressures after taking Drug B (assume the data are parametric and homoscedastic)? a) Wilcoxon signed rank test b) Chi-squared test c) Independent t-test d) Paired t-test e) None of the above
Paired t-test
A study is comparing nicotine patches and nicotine gum. The primary outcome is the rate of smoking cessation (i.e., proportion of subject who can quit). What is the most appropriate study design to determine which treatment is more effective? a) Factorial design b) Crossover design c) Parallel-group design d) Case-control study None of the above
Parallel-group design
A study is comparing nicotine patches and nicotine gum. The primary outcome is the rate of smoking cessation (i.e., proportion of subject who can quit). What is the most appropriate study design and statistical test to determine which treatment is more effective? a) Parallel-group; t-test b) Crossover; chi-square test c) Parallel-group; chi-square or Fisher's exact d) Crossover; paired t-test
Parallel-group; chi-square or Fisher's exact
A study is conducted to determine the differences in ulcer relapse rates between 2 anti-Helicobacter pylori drug regimens. The study is conducted on an intention-to- treat basis (ITT). Which of the following is FALSE with regard to ITT studies? a) The researchers are forced to make assumptions about the missing data, which is a potential source of error b) Per-protocol analyses utilize data from all patients entered into the study, regardless of whether they completed the study or not. c) Last-observation-carried forward (LOCF) is a common technique used in ITT analyses d) A and B e) All of the above
Per-protocol analyses utilize data from all patients entered into the study, regardless of whether they completed the study or not.
A new drug, Superstatin, is indicated for treating dyslipidemia; however, the FDA is concerned that this drug may cause liver toxicity. There were a few reports of liver toxicity before the drug came to the market; however, not enough reports existed to conclude an increased risk of liver toxicity. Which one of the following study designs is best suited to identify whether an increased risk of liver toxicity exists with superstatin? a) Randomized controlled clinical trial b) Prospective cohort study c) Case-control study d) Cross-sectional study
Prospective cohort study
Which of the following research designs would be the MOST optimal in terms of controlling the study and producing valid results for a clinical trial comparing two drugs? a) Prospective, randomized, double-blind parallel study Prospective experimental with historical control, open-label, comparative study b) Prospective experimental with historical control, open-label, comparative study c) Observational, double-blind parallel study d) Retrospective, parallel, longitudinal, open-label study e) A and C
Prospective, randomized, double-blind parallel study
The most effective method of controlling extraneous variables is by: a) Analysis of covariance b)bMatching c) Randomization d) Use control group e) None of the above
Randomization
A study was conducted to evaluate an antibiotic in the treatment of possible bacteremia. Five hundred children with fever but no focal infection were randomly assigned to the antibiotic or to a placebo. All patients were re-evaluated after 48 hours. The design used in this study is best described as a: a) Randomized clinical trial b) Placebo-controlled trial c) Controlled clinical trial d) Cohort study
Randomized clinical trial
A study is conducted to compare the efficacy of two medications (Drug A and Drug B) for the treatment of hypertension. One hundred patients are enrolled in the study (50 receiving Drug A and 50 receiving Drug B). Which of the following terms BEST describes patients receiving the study medications? a) Population b) Sample c) Experimental group d) Control group e) None of the above
Sample
In some non-randomized studies, patients are assigned to certain treatment groups based on some characteristic that they possess, which could affect the outcome of the study. This type of bias is known as: a) Volunteer bias b) Contamination bias c) Selection bias d) Correlation bias e) None of the above
Selection bias
The proportion of people with disease, who have positive test results is referred to: a) Specificity b) Sensitivity c) Responsiveness d) None of the above
Sensitivity
A case-control study was conducted in Kenya to test for the effectiveness of insecticide bed nets as a way to reduce malaria. People who developed Malaria were matched against those who did not and whether or not they slept with bednets was recorded. Results are given in the table below. The investigators use the Chi-square test to see if there is an association between use of bednets and the contraction of malaria. If we have rejected the null hypothesis, we conclude a) There is no association between use of bednets and malaria b) We could have made a type II error c) Since the study wasn't a randomized controlled experiment, the use of bednets won't necessarily lower the risk of malaria, since there could be other variables influencing the association. d) Since the study was a case control study we conclude that bednets will lower the risk of malaria.
Since the study wasn't a randomized controlled experiment, the use of bednets won't necessarily lower the risk of malaria, since there could be other variables influencing the association.
Consider a data set of the scores of students on a very easy exam in which most score very well but a few score very poorly. What shape would you expect a histogram of this data set to have? a) Symmetric b) Skewed to the left c) Skewed to the right d) Bimodal
Skewed to the left
The standard deviation of a sampling distribution is called a: a) Sampling error b) Standard error c) Variance d) Mean Square e) Coefficient of variation
Standard error
Non-probability sampling includes all of the following except: a) Convenience sampling b) Stratified sampling c) Purposive sampling d) Quota sampling e) Snowball sampling
Stratified sampling
The term "internal validity" is defined as: a) Being able to take the results of a particular study and apply them to the population as a whole b) The sensitivity of a study in being able to detect change as it occurs c) The ability of a study to support causal inference between the effects of the independent variable on the dependent variable d) None of the above
The ability of a study to support causal inference between the effects of the independent variable on the dependent variable
CASE D. The following 3 questions are based on CASE D A study comparing the efficacy of two H2 blockers in the treatment of patients with duodenal ulcers was conducted. The study determined that Drug A had a 90% cure rate, and that Drug B had an 84% cure rate. The following information is supplied: (Curediff) = 6% (Curediff = Drug A - Drug B = 90% - 84%) (95%CIdiff) = +2%, +10% (95%CIdiff = 95% confidence interval for the difference in ulcer cure rates) Based on the 95% confidence interval for the difference, which of the following is TRUE? a) The null hypothesis is accepted b) The alternative hypothesis is accepted c) The data is insufficient to determine whether we can accept or reject the null hypothesis d) Drug A is statistically superior compared to Drug B, but clinically we are 95% confident that there is a possibility that they have similar clinical efficacy e) None of the above
The alternative hypothesis is accepted
If you decided to reject the null hypothesis but it was in fact true, you a) Made a correct decision b) Made both a type I and type II error c) Made a type I error d) Made a type II error
The amount of Type II error is not evaluated because the null hypothesis is rejected and a difference between groups exists
When p-values are statistically significant, the following conclusions can be reached a) The amount of Type II error is not evaluated because the null hypothesis is rejected and a difference between groups exists b) The amount of Type I error is excessive. c) The test might not have had enough power to produce a statistically significant result d) None of the above
The amount of Type II error is not evaluated because the null hypothesis is rejected and a difference between groups exists
When p values are statistically significant, the following conclusion(s) can be reached: a) The amount of Type I error is excessive and null hypothesis is accepted b) The amount of Type II error is not evaluated, because the null hypothesis is rejected and differences between groups exist c) There is a clinically significant difference between the groups d) B and C e) None of the above
The amount of Type II error is not evaluated, because the null hypothesis is rejected and differences between groups exist
An analgesic medication was compared to an identical appearing placebo by random assignment to separate treatment groups. Pain was measured on a scale where 0 = none, 1 = mild, 2 = moderate and 3 = severe. Pain was measured at baseline to determine if the two groups were similar. Before the data were collected, the investigators stated that the level of pain 8 hours after a single dose of analgesic was the primary end point. Nevertheless, they measured pain every hour after the dose for 8 hours. The investigator presented a statistical test that was appropriate for the level of measurement to compare the pain in the two treatment groups at baseline. The pain measurements within each group were not identical, but the p-value for the baseline comparison was 0.22. Which of the following could you conclude from this information? a) The baseline differences in pain between the two groups could be due to sampling variation b) The differences at baseline would not cause the groups to be difference at 8 hours c) The study had inadequate power to compare pain after 8 hours d) The likelihood that the observed differences would occur due to sampling variation was less than 5%.
The baseline differences in pain between the two groups could be due to sampling variation
Results of randomized, double-blind, controlled clinical trial revealed that the difference in rehospitalization rates between the intervention group and the control group is 6% (p=0.01). The authors conclude that there is a statistically significant difference between the groups. Which of the following statements is TRUE? a) The chance of making type I error is 5 in 100 b) The trial does not have enough power c) There is a high likelihood of having made a type II error d) The chance of making an alpha error is 1 in 100 e) None of the above
The chance of making an alpha error is 1 in 100
CASE D. The following 3 questions are based on CASE D A study comparing the efficacy of two H2 blockers in the treatment of patients with duodenal ulcers was conducted. The study determined that Drug A had a 90% cure rate, and that Drug B had an 84% cure rate. The following information is supplied: (Curediff) = 6% (Curediff = Drug A - Drug B = 90% - 84%) (95%CIdiff) = +2%, +10% (95%CIdiff = 95% confidence interval for the difference in ulcer cure rates) Based on data from the 95% confidence interval for the difference, which of the following is TRUE? a) Drug A is always superior to Drug B in the population of patients with ulcers b) The confidence interval states we are 95% confident that the ulcer cure rates for Drug A is superior to Drug B in the population c) We are 95% confident that Drug A and Drug B may have equal cure rates in the population d) A and B e) All of the above
The confidence interval states we are 95% confident that the ulcer cure rates for Drug A is superior to Drug B in the population
CASE B. The following 3 questions are based on CASE B A study is developed to compare the efficacy in lowering diastolic blood pressure (DBP) between 2 different antihypertensives. The authors provide the following information: Alpha < 0.05 Beta = 0.2 Power = 80% Delta = 5 mm Hg (also known as the expected effects size) Sigma = 10 mm Hg N = 120 patients/group The study results indicate that on average, Drug A can reduce BP by 20 mm Hg, and Drug B can reduce BP by 8 mm Hg. The p value for this comparison is p = 0.01. NOTE: Assume that a reasonable clinical difference in blood pressure reduction is 5 mm Hg between groups and that the population variance is expected to be 10 mm Hg. Which of the following is a TRUE statement (based on data from CASE B)? a) The difference in DBP is statistically significant because the amount of Type I error is less than alpha (the level of significance) b) The amount of Type II error is excessive because the sample size is too small c) Statistical power could only detect differences of 12 mm Hg or larger between groups (with 80% power) d) B and C e) None of the above
The difference in DBP is statistically significant because the amount of Type I error is less than alpha (the level of significance)
Which of the following is FALSE with respect to the term "random chance" and "systematic error"? a) Random chance cannot be predicted nor controlled by using appropriate research methods b) The effect of random chance can be reduced by the use of appropriate choice of statistical tests c) Outcomes of clinical trials may be affected by random chance d) Use of appropriate methodology can reduce the amount of bias in a clinical trial e) Biases may randomly affect the outcome of a trial, making interpretation difficult f) Both systematic error and random chance can affect the outcomes of a study simultaneously
The effect of random chance can be reduced by the use of appropriate choice of statistical tests And Biases may randomly affect the outcome of a trial, making interpretation difficult
Determine which samples are dependent. a) The effectiveness of Prilosec for treating heartburn is tested by measuring gastric acid secretion in a group of patients treated with Prilosec and another group of patients given a placebo b) The effectiveness of Prilosec for treating heartburn is tested by measuring gastric acid secretions in patients before and after drug treatment. The data consist of before/after measurements for each patient c) The flu vaccine is tested by treating one group of subjects with the vaccine while another group of subjects is give placebos d) None of the samples are dependent
The effectiveness of Prilosec for treating heartburn is tested by measuring gastric acid secretions in patients before and after drug treatment. The data consist of before/after measurements for each patient
A physician at HMC wants to start all of his patients admitted to the ICU on a proton pump inhibitor (PPI). He states a recent study of hospitalized patients found that PPI improve survival when used for stress ulcer prophylaxis. You as a student pharmacist realize this will increase the pharmacy's budget considerably and want to evaluate the evidence. Which one of the following is true? a) The inclusion and exclusion criteria should be evaluated to determine whether the patient population is similar to your patient population before using the study results to make a decision b) If a significant difference is found between the two groups, then the possibility of a type II error must be considered. c) The methods used to blind the study are not important because the outcome was objective. d) It is not important to review the competency of the authors by reviewing their affiliations and credentials.
The inclusion and exclusion criteria should be evaluated to determine whether the patient population is similar to your patient population before using the study results to make a decision
In a meta-analysis of RCT examining the effects of antihypertensive drugs, investigators found that the OR for treatment with low-dose diuretics compared with beta-blockers for CV disease events was 0.86 (95%CI, 0.77-0.97). Which one of the following statements is the most appropriate interpretation of these findings? a) Treatment of hypertension with low-dose diuretics was 14% more effective in preventing CV disease events than treatment with beta-blockers. b) Treatment of hypertension with beta-blockers was 14% more effective in preventing CV disease events than treatment with low-dose diuretics. c) The difference observed between treatment with beta-blockers and low-doses of diuretics was not statistically significant. d) The odds of developing CV events when treating hypertension with low-dose diuretics was lower than treatment with beta-blockers
The odds of developing CV events when treating hypertension with low-dose diuretics was lower than treatment with beta-blockers
In a placebo-controlled trial of the use of oral aspirin-dipyridamole to prevent arterial restenosis after coronary angioplasty, 38% of patients receiving the drug had restenosis, and 39% of patients receiving placebo had restenosis. In reporting this finding, the authors stated that p>0.05, which means that a) Chances are greater than 1 in 20 that a difference would again be found if the study were repeated b) The probability is less than 1 in 20 that a difference this large could occur by chance alone c) The probability is greater than 1 in 20 that a difference this large could occur by chance alone d) Treated patients were 5% less likely to have restenosis e) The chance is 95% that the study is correct
The probability is greater than 1 in 20 that a difference this large could occur by chance alone
In a placebo-controlled trial of the use of aspirin and dipyridamole to prevent arterial restenosis after coronary angioplasty, 38% of patients receiving the treatment had restenosis, and 39% of patients receiving placebo has restenosis. In reporting this finding, the authors stated that P > 0.05. This means: a) The chances are greater than 1 on 20 that a difference would be found again in the study were repeated. b) The probability is less than 1 in 20 that a difference this large could occur by chance alone. c) The probability is greater than 1 in 20 that a difference this large could occur by chance alone. d) The chance is 95% that the study is correct.
The probability is greater than 1 in 20 that a difference this large could occur by chance alone.
CASE C. The following 3 questions are based on CASE C A study is conducted to compare the clinical efficacy of 2 antibiotics for the treatment of urinary tract infections. The authors provide the following information: Alpha < 0.05 Beta = 0.2 Delta = 25% (difference in antibiotic cure rates) N = 20 patients/group The results indicate that Drug A was efficacious in 92% of the patients, and Drug B was efficacious in 86% of the patients. The p value for this comparison is p = 0.33. NOTE: Assume that a reasonable clinical difference between groups in terms of antibiotic efficacy is 10%. Which of the following is a TRUE statement (based on data from CASE C)? a) The result indicates a statistically insignificant finding, and the null hypothesis is accepted b) The result is statistically insignificant and clinically significant c) The p value indicates that there is insufficient power to evaluate the data d) A and B e) All of the above
The result indicates a statistically insignificant finding, and the null hypothesis is accepted
CASE B. The following 3 questions are based on CASE B A study is developed to compare the efficacy in lowering diastolic blood pressure (DBP) between 2 different antihypertensives. The authors provide the following information: Alpha < 0.05 Beta = 0.2 Power = 80% Delta = 5 mm Hg (also known as the expected effects size) Sigma = 10 mm Hg N = 120 patients/group The study results indicate that on average, Drug A can reduce BP by 20 mm Hg, and Drug B can reduce BP by 8 mm Hg. The p value for this comparison is p = 0.01. NOTE: Assume that a reasonable clinical difference in blood pressure reduction is 5 mm Hg between groups and that the population variance is expected to be 10 mm Hg. Which of the following is TRUE with regards to the clinical significance or clinical insignificance of the result (based on data from CASE B)? a) Clinical significance was achieved, because the null hypothesis was accepted, and the difference of 5 mm Hg between groups is clinically significant b) Clinical significance was not achieved, because a difference of 5 mm Hg is not clinically significant c) Clinical significance should not be evaluated, since the null hypothesis was accepted d) The result is clinically significant, because the null hypothesis was rejected, and the difference of 12 mm Hg is clinically significant e) None of the above
The result is clinically significant, because the null hypothesis was rejected, and the difference of 12 mm Hg is clinically significant
A study is conducted to compare the clinical efficacy of 2 antibiotics for the treatment of pneumonia. The patients are randomly assigned to receive either Drug A or Drug B. The main dependent variable is mortality over a 14 day period. The authors provide the following information: Alpha < 0.05; Beta = 0.2; Delta = 4% (for mortality); Std Proportion = 10%; N = 50 patients/group. The results indicate that mortality in patients who received Drug A was 12% compared to Drug B which was 14%. The p value for this comparison is p = 0.15. Assume that a reasonable clinical difference between groups in terms of mortality is 5%. Which of the following is a TRUE statement? a) The difference in antibiotic mortality between the groups was 2%, and indicates that clinical significance was achieved b) There is sufficient statistical power to detect a reasonable clinical difference but the standard proportion does not support sufficient statistical power c) The statistical power is adequate to detect a reasonable clinical difference between the groups d) None of the above
The statistical power is adequate to detect a reasonable clinical difference between the groups
CASE C. The following 3 questions are based on CASE C A study is conducted to compare the clinical efficacy of 2 antibiotics for the treatment of urinary tract infections. The authors provide the following information: Alpha < 0.05 Beta = 0.2 Delta = 25% (difference in antibiotic cure rates) N = 20 patients/group The results indicate that Drug A was efficacious in 92% of the patients, and Drug B was efficacious in 86% of the patients. The p value for this comparison is p = 0.33. NOTE: Assume that a reasonable clinical difference between groups in terms of antibiotic efficacy is 10%. Which of the following is a TRUE statement (based on data from CASE C)? a) The difference in antibiotic efficacy between the groups was 6%, and indicates that clinical significance was achieved b) The statistical power is sufficient to detect a difference of 25% between the groups, but this difference exceeds what a reasonable clinical difference should be c) The study has sufficient power to detect a efficacy difference of 10% between the groups d) All of the above e) None of the above
The statistical power is sufficient to detect a difference of 25% between the groups, but this difference exceeds what a reasonable clinical difference should be
A clinical trial is designed to compare INR measurements during treatment with brand-name and generic warfarin. Mean INR during brand-name treatment was 2.45, and mean INR during generic treatment was 2.51 (p=0.0001; paired t-test). How should the results be interpreted? a) There is a clinically significant difference between the two formulations b) There is a 0.01% chance that a Type II error has occurred c) There is a statistically significant difference between the two treatments d) No conclusion can be drawn because the wrong statistical test was used
There is a statistically significant difference between the two treatments
Researchers measure cholesterol levels in a sample of patients in New Zealand and Asia and find the following results: a) There is no statistically significant difference in mean cholesterol levels between the 2 populations b) There is a statistically significant difference in mean cholesterol level in the Asian population as compared to the New Zealand population c) There is a statistically significant higher mean cholesterol level in the New Zealand sample as compared to the Asian sample. d) There is a statistically significant higher mean cholesterol level in the New Zealand population as compared to the Asian population.
There is a statistically significant higher mean cholesterol level in the New Zealand population as compared to the Asian population.
CASE C. The following 3 questions are based on CASE C A study is conducted to compare the clinical efficacy of 2 antibiotics for the treatment of urinary tract infections. The authors provide the following information: Alpha < 0.05 Beta = 0.2 Delta = 25% (difference in antibiotic cure rates) N = 20 patients/group The results indicate that Drug A was efficacious in 92% of the patients, and Drug B was efficacious in 86% of the patients. The p value for this comparison is p = 0.33. NOTE: Assume that a reasonable clinical difference between groups in terms of antibiotic efficacy is 10%. Which of the following are POSSIBLE conclusions that can be drawn from this data? a) There is a difference in clinical efficacy between the drugs b) There may be a difference in efficacy between the drugs, but the power / delta assessment indicated that there was insufficient power to detect a reasonable clinical difference c) It can be stated with confidence that there is no difference in efficacy between the drugs because the power / delta assessment indicated that the study had sufficient power to detect a difference if a difference existed, but no difference was found. d) A and B e) None of the above
There may be a difference in efficacy between the drugs, but the power / delta assessment indicated that there was insufficient power to detect a reasonable clinical difference
Which one of the following describes the most important limitation of composite outcomes? a) They allow the counting of many events in the same patient. b) They assume that all outcomes are equally important. c) There is insufficient power to detect treatment effects on the individual components of the composite outcome. d) They are unable to classify all outcomes precisely. e) None of the above
They assume that all outcomes are equally important.
Many cardiovascular trials now use composite outcomes such as hospitalization for heart failure, stroke, MI, or CV death. Which one of the following best describes why composite outcomes are useful? a) They can provide more data on adverse effects. b) They add together outcome events for a single patient to form a single endpoint for a study. c) They reduce the complexity of describing treatment effects. d) They can reduce sample size requirement. e) None of the above
They can reduce sample size requirement.
An early-phase clinical trial of 50 subjects was designed to evaluate a new drug known to increase HDL-C levels. The purpose of the trial was to compare the new drug's ability to increase HDL-C with that of lifestyle modifications (active control group). at the beginning of the study, the mean baseline HDL-C was 37 mg/dL in the active control group and 38 mg/dL in the new drug group. At the end of the 3- month trial, the mean HDL-C was 44 mg/dL for the control group and 49 mg/dL for the new drug group. The p-value for the comparison at 3 months was 0.08. Which of the following statements is the BEST interpretation of these results? a) An a priori alpha of less than 0.10 would have made the study more clinically useful b) The new drug and active control appear to be equally efficacious in increasing HDL-C c) The new drug is better than lifestyle modifications because it raises HDL-C to a greater extent d) This study is potentially underpowered e. A paired t-test is appropriate test to compare between two group at the end of the 3-month trial.
This study is potentially underpowered e. A paired t-test is appropriate test to compare between two group at the end of the 3-month trial.
Describing the results of the study, which of the following statements would be most accurate? Diuretics OR = 1 Beta-blockers OR = 1.09 (0.74-1.63) Beta-blockers + diuretics OR = 0.97 (0.62-1.52) CCB OR = 1.58 (1.04-2.39) CCB + diruestics = 1.70 (0.97-2.99) a) Use of CCBs is associated with a 6-fold increase in odds of MI b) Use of CCBs was associated with a 60% increase in the odds of a first MI c) Beta-blockers and diuretics are the safest combination for treating hypertension d) CCBs cause more MIs than diuretics or -blockers
Use of CCBs was associated with a 60% increase in the odds of a first MI
When we test H0: μ1 - μ2 = 0 vs. H1: μ1 - μ2≠0, we get a P-value of 0.02. What would the decision be at a significance level of α = 0.05. a) We would decide to reject the null hypothesis. We would have sufficient evidence that there was a difference between the two population means b) We would decide to reject the null hypothesis. We would have sufficient evidence that there was no difference between the two population means c) We would decide to not to reject the null hypothesis. We would have sufficient evidence that there was no difference between the two population means d) We would decide not to reject the null hypothesis. We would have sufficient evidence that there a difference between the two population means
We would decide to reject the null hypothesis. We would have sufficient evidence that there was a difference between the two population means
Dr. Supakit conducted a study to compare Drug A and Drug B for treating N/V associated with pregnancy. Drug A has been used for many years and has a large evidence base showing efficacy and safety. Drug B was recently introduced to treat N?V associated with chemotherapy, but has not been studied by pregnant patients with N/V. Patients were randomized to one of these 2 drugs. The primary outcome was patients' ranking of their N/V 3 hours after taking the drug. N/V was graded using the following scale: 0=no nausea, 2=moderate nausea, 3=severe nausea, and 4=vomiting. Which is the best statistical test to test for differences between two drugs? a) Wilcoxon rank sum test b) Wilcoxon signed rank test c) Student's t-test d) Paired student's t-test
Wilcoxon rank sum test
Which of the following study designs is best suited for assessing an exposure-disease relationship when the outcome is rare and/or when the latency period involved is relatively long? a) Cross-sectional b) Prospective cohort c) Retrospective cohort d) case-control
case-control
