Epi Module 3 Practice Questions
Children age 6-9 months were randomly assigned to receive either placebo or a beverage containing a zinc supplement. Morbidity data were collected daily and focused on the presence of diarrhea and/or respiratory infections. What is the best description of this type of study? 1Clinical trial 2Cohort study 3Case-control study 4Cross-sectional study 5Case series
1 - This study is a good example of a community-based clinical trial. In this study, both the investigators and the subjects were blinded as to whether the individual patient was receiving the active treatment (zinc supplementation) or placebo. The study subjects were then followed through time for the primary outcomes of interest (diarrhea and respiratory infections) so that the efficacy of the treatment could be evaluated. While this study did involve a "cohort" of patients, a true cohort study is observational in nature, whereas clinical trials involve some type of intervention or treatment.
Religion is considered what type of variable? 1 Nominal 2 Ordinal 3 Interval 4 ratio
1- The correct response is nominal. Nominal variables are discrete categories without any ordering. They are qualitative variables. Examples are religion, gender, marital status, and race. Ratio variables are those numbers which, when divided by each other, give meaningful ratios. They are quantitative variables, and they generally include 0 as their lowest possible value. Examples are height, weight, age, and pulse. Interval variables are those numbers which, when subtracted from each other, giver meaningful values. They are quantitative variables, and they generally do not include 0 as their lowest possible value. The difference between values is the important factor. One of the most well known is temperature in Centigrade or Fahrenheit. 60°F is 40° more than 20°, but it is not 3 times as warm. If temperatures were expressed in degrees Kelvin, however, they would be ratio variables, since the lowest value of the Kelvin scale is zero (absolute zero); 60°K is 3 times as warm as 20°K. Time measurements are also interval variables. Ordinal variables are discrete categories that are ordered. They are qualitative variables. Examples are pain scales, cancer staging, and letter course grades. While they may be numbers, they cannot be divided by or subtracted from each other to give meaningful results.
What test parameter best describes the extent to which a test approximates the real value of that which is measured? 1 Accuracy 2 Reliability 3 Precision 4 Validity
1- The mode is the most commonly occurring value in a series of data. Reliability is a measure of the reproducibility of a test over different conditions. The four most common types are inter-observer reliability, intra-observer reliability, split-sample reliability, and repeat testing reliability. Accuracy is a measure of the extent to which a test approximates the real value of that which is measured. New tests are measured against the gold standard, if one exists. Validity is the assessment of the degree to which a test measures that for which it was designed. In other words, does it reflect the outcome of interest or other outcomes? Precision is the degree to which a measurement is not subject to random variation.
In 1994, Nichol et al. carried out a study in which working adults between the ages of 18 and 64 were enrolled in a study of the effectiveness of influenza vaccine. A total of 849 subjects were enrolled, of which 424 received the active vaccine, and 425 received the placebo vaccine. The authors followed the patients forward in time and recorded the number of episodes of respiratory illness and missed days from work. The authors found that vaccination against influenza provided substantial benefits, even for healthy, working adults. Which of the following best describes this study design 1A clinical trial 2A cohort study 3A case-control study 4A cross-sectional study 5A case series
1- This is a good example of a clinical trial. In this study, healthy adults were enrolled in a randomized trial in which they received either an active influenza vaccine or a placebo vaccination. By following the patients forward in time, the investigators will be able to evaluate the safety and efficacy of this vaccine.
Myocardial infarction pain scale (1-10) is considered which type of variable listed below? 1 Nominal 2 Ordinal 3 Interval 4 Ratio
2
What test parameter best describes the reproducibility of a test? 1 Accuracy 2 Reliability 3 Precision 4 Validity
2 - Reliability is a measure of the reproducibility of a test over different conditions. The four most common types are inter-observer reliability, intra-observer reliability, split-sample reliability, and repeat testing reliability Accuracy is a measure of the extent to which a test approximates the real value of that which is measured. Validity is the assessment of the degree to which a test measures what it was designed to measure. In other words, does it reflect the outcome of interest or other outcomes? Precision is the degree to which a measurement is not subject to random variation.
A 39-year-old female breast cancer patient comes into your office to discuss a new form of treatment. She underwent lumpectomy and radiation therapy 6 months ago, but is concerned about her cancer returning. She has been actively searching for different treatment options and has learned about a Phase II clinical trial of a new breast cancer vaccine. She wants to know what a 'Phase II' trial is. What would you explain to her about a Phase II trial and what it determines? 1 If the new treatment is safe 2 The best way to give the new treatment 3 If the new treatment is efficacious 4 If the new treatment is more effective than current treatments 5 If the new treatment is safer than current treatments
3 - Phase II clinical trials are conducted to determine if a new form of treatment has any effect against a particular disease. Phase II studies are done only after Phase I trials are completed. The safety, maximum tolerated dose, and best method of administering a new treatment is explored in Phase I studies (which usually involve small numbers of participants). While determining effectiveness is not an objective of Phase I studies, some patients may still receive some benefit from them Phase III clinical trials are conducted after efficacy is proven in Phase II trials. These trials compare new treatments with the current standards, and may look at efficacy (if side effect profiles appear similar) or compare safety profiles (if the efficacy is similar). In practice, most Phase III trials compare both parameters.
There are no Phase 0 clinical trials. Temperature is considered which type of variable listed below? 1Nominal 2Ordinal 3Interval 4Ratio
3 - Ratio variables are those numbers which, when divided by each other, give meaningful ratios. They are quantitative variables, and generally include zero as their lowest possible value. Examples are height, weight, age, and pulse. In other words, we could say that someone 6 feet tall is twice as tall as someone with a height of 3 feet. Nominal variables are discrete categories without any ordering. They are qualitative variables. Examples are religion, gender, marital status and race. Thus, one variable cannot be said to be "more" or "less" than another, just different. Interval variables are those numbers which, when subtracted from each other, giver meaningful values. They are quantitative variables, and generally do not include zero as their lowest possible value. The difference between values is the important factor. One of the most well known is temperature in Centigrade or Fahrenheit. Thus, 60° F is 40° more than 20° , but is not three times as warm. If temperatures were expressed in degrees Kelvin, however, they would be ratio variables, since the lowest value of the Kelvin scale is zero (absolute zero). Thus, 60° K is three times as warm as 20° K. Time measurements are also interval variables. Ordinal variables are discrete categories which are ordered. They are qualitative variables. Examples are pain scales, cancer staging, and letter course grades. While they may be numbers, they cannot be divided by or subtracted from each other to give meaningful results. One variable can be said to be "more" or "less" than another. Thus, on a pain scale, "8" represents more pain than "4", but is not necessarily twice as bad as "4".
A grading for actual activity level (1-5, with 1 = sedentary and 5 = very active) What study design is this? 1Case-control study 2Cohort study 3Randomized clinical trial 4Crossover study 5Cross-sectional
3 - There are 2 study arms present. In the 1st one, only the conventional therapy is present, and in the 2nd, diet and exercise are added to conventional therapy; therefore, this is an experimental study. The patients are assigned to only 1 of the 2 study arms. Due to the nature of the intervention (diet plus exercise), patients are unblinded to their study group. This is a randomized clinical trial. In a crossover study, patients are assigned to one of the study arms for a period of time and then assigned to the other study arm for the same length of time The other study designs mentioned are all observational studies. In case-control studies, people with and without a specific outcome are chosen. Looking backward in time, one tries to detect possible causes or risk factors In a cohort study, people are selected and followed over a period of time. At the beginning of the study, people are defined as being exposed, or not exposed, to certain risk factors. They are observed over time for the development of outcome. The outcome is then compared to exposure to risk factors In cross-sectional studies, data is collected at one time; large government surveys are good examples of cross-sectional studies.
A 51-year-old man with metastatic colon cancer comes into your office for a follow-up visit. He has been treated with chemotherapy, but his last CT scan showed he still had several large metastases in his liver; treatment was stopped. He tells you about a clinical trial for a new anti-cancer drug he recently found while searching on the Internet. He does not remember much about the study other than it is looking at how effective the drug is, and only 50 people will be allowed to participate. What is the most likely phase trial of this drug? 1 Phase 0 trial 2 Phase I trial 3 Phase II trial 4 Phase III trial 5 Phase IV trial
3- Following laboratory and animal testing, any new drug or treatment must undergo 3 phases of clinical trials prior to approval by the FDA (for use in the United States). Phase I clinical trials are the 1st studies of a treatment to be conducted in humans. The aim of a Phase I study is to evaluate the safety of the drug by determining the maximum tolerated dose and the best way to administer it. Phase I studies involve small numbers of patients (usually 10 to 30), and may involve patients with different diseases (such as different kinds of cancer). All patients are closely monitored for side effects. Once a drug is shown to be safe at a certain dose level in a Phase I study, a Phase II clinical trial is conducted, to determine if the drug is effective at that dose. All patients receive the same dose and schedule in Phase II trials, and there are no placebos. Phase II trials generally enroll fewer than 100 patients. If efficacy is demonstrated in a Phase II study (i.e., a certain minimum percentage of patients benefit from the treatment), a Phase III clinical trial may be started. Phase III trials compare new treatments with those already established as standard treatment. When possible, these studies are randomized and double-blinded, to protect against bias. Phase III trials generally involve hundreds of patients to provide enough statistical power. Treatments demonstrating benefits in Phase III trials are generally approved for commercial marketing. Phase IV clinical trials are considered to be post-marketing studies, as they involve treatments that are already approved for use. Phase IV studies usually evaluate new indications, or new dosing schedules, for existing treatments. There are no Phase 0 clinical trials.
A colon cancer screening study is being conducted in Nottingham, England. Individuals 50 to 75 years old will be screened with the Hemoccult test. In this test, a stool sample is tested for the presence of blood. The Hemoccult test has a sensitivity of 70% and a specificity of 75%. If Nottingham has a prevalence of 12/1,000 for colon cancer, what is the positive predictive value of the test? _____
3.3%
which a measurement is not subject to random variation. A 66-year-old man with hormone-refractory prostate cancer comes into your office for a follow-up visit. You suggest he consider participating in a clinical trial, which is designed to compare 2 different chemotherapy regimens in men with his disease. The trial is being conducted at cancer centers throughout the country, and will enroll about 400 patients. What is the most likely phase trial of this drug? 1 Phase 0 trial 2 Phase I trial 3 Phase II trial 4 Phase III trial 5 Phase IV trial
4
What does the null hypothesis state? 1 There is a significant difference between populations tested. 2 The difference between populations is not attributable to chance. 3 The difference between populations is due to a particular factor. 4 There is no significant difference between populations tested.
4 - The null hypothesis states that there is no significant difference between the populations being tested and that any difference that is found is attributable to chance. It is tested against the alternative hypothesis, which is that there is a significant difference between the populations tested.
What test parameter best describes how well a test measures what it was designed to measure? 1 Accuracy 2 Reliability 3 Precision 4 Validity
4 - Validity is the assessment of the degree to which a test measures what it was designed to measure. In other words, does it reflect the outcome of interest or other outcomes? Reliability is a measure of the reproducibility of a test over different conditions. The four most common types are inter-observer reliability, intra-observer reliability, split-sample reliability, and repeat testing reliability. Accuracy is a measure of the extent to which a test approximates the real value of that which is measured. Precision is the degree to which a measurement is not subject to random variation.
Height is considered what type of variable? 1 Nominal 2 Ordinal 3 Interval 4 Ratio
4- Ratio variables are those numbers which, when divided by each other, give meaningful ratios. They are quantitative variables, and they generally include 0 as their lowest possible value. Examples are height, weight, age, and pulse. Nominal variables are discrete categories without any ordering. They are qualitative variables. Examples are religion, gender, marital status, and race. One variable cannot be said to be "more" or "less" than another, just different Interval variables are those numbers which, when subtracted from each other, give meaningful values. They are quantitative variables, and they generally do not include 0 as their lowest possible value. The difference between values is the important factor. One of the most well known is temperature in Centigrade or Fahrenheit. 60° F is 40° more than 20°, but it is not 3 times as warm. If temperatures were expressed in degrees Kelvin, however, they would be ratio variables since the lowest value of the Kelvin scale is 0 (absolute zero);60° K is 3 times as warm as 20°K. Time measurements are also interval variables Ordinal variables are discrete categories that are ordered. They are qualitative variables. Examples are pain scales, cancer staging, and letter grades. While they may be numbers, they cannot be divided by or subtracted from each other to give meaningful results.
A physical examination was used to screen for breast cancer in 2,500 women with biopsy-proven adenocarcinoma of the breast and in 5,000 age- and race-matched control women. The results of the physical examination were positive (i.e., a mass was palpated) in 1,800 cases and in 800 control women, all of whom showed no evidence of cancer at biopsy. The positive predictive value of the physical examination was: ______
69.2%
A physical examination was used to screen for breast cancer in 2,500 women with biopsy-proven adenocarcinoma of the breast and in 5,000 age- and race-matched control women. The results of the physical examination were positive (i.e., a mass was palpated) in 1,800 cases and in 800 control women, all of whom showed no evidence of cancer at biopsy. The sensitivity of the physical examination was: ______
72.0%
A physical examination was used to screen for breast cancer in 2,500 women with biopsy-proven adenocarcinoma of the breast and in 5,000 age- and race-matched control women. The results of the physical examination were positive (i.e., a mass was palpated) in 1,800 cases and in 800 control women, all of whom showed no evidence of cancer at biopsy. The specificity of the physical examination was: ______
84.0%
A new screening program was instituted in a certain country. The program used a screening test that is effective in detecting cancer Z at an early stage. Assume that there is no effective treatment for this type of cancer and therefore that the program results in no change in the usual course of the disease. Assume also that the rates noted are calculated from all known cases of cancer Z and that there were no changes in the quality of death certification of this disease. What will happen to the apparent incidence rate of cancer Z in the country during the first year of this program? a. Incidence rate will increase b. Incidence rate will decrease c. Incidence rate will remain constant
A
A new screening program was instituted in a certain country. The program used a screening test that is effective in detecting cancer Z at an early stage. Assume that there is no effective treatment for this type of cancer and therefore that the program results in no change in the usual course of the disease. Assume also that the rates noted are calculated from all known cases of cancer Z and that there were no changes in the quality of death certification of this disease. What will happen to the apparent prevalence rate of cancer Z in the country during the first year of this program? a. Prevalence rate will increase b. Prevalence rate will decrease C. Prevalence rate will remain constant
A
A randomized trial comparing the efficacy of two drugs showed a difference between the two (with a P value < .05). Assume that in reality, however, the two drugs do not differ. This is therefore an example of the following: a. Type I error (α error) b. Type II error (β error) c. 1 − α d. 1 − β e. None of the above
A
Choose the best study design from the list below for each of the following research questions. Each study design can only be used once. a. Ecologic study b. Cross-sectional study c. Case-control study d. Prospective cohort e. Randomized trial _____ A researcher believes that the county- level rate of hospitalization for cardiovascular disease will increase with increasing levels of outdoor air pollution.
A
A colon cancer screening study is being conducted in Nottingham, England. Individuals 50 to 75 years old will be screened with the Hemoccult test. In this test, a stool sample is tested for the presence of blood. If the Hemoccult test result is negative, no further testing is done. If the Hemoccult test result is positive, the individual will have a second stool sample tested with the Hemoccult II test. If this second sample also tests positive for blood, the individual will be referred for more extensive evaluation. What is the effect on net sensitivity and net specificity of this method of screening? a. Net sensitivity and net specificity are both increased b. Net sensitivity is decreased and net specificity is increased c. Net sensitivity remains the same and net specificity is increased d. Net sensitivity is increased and net specificity is decreased
B
A diagnostic test has been introduced that will detect a certain disease 1 year earlier than it is usually detected. Which of the following is most likely to happen to the disease within the 10 years after the test is introduced? (Assume that early detection has no effect on the natural history of the disease. Also assume that no changes in death certification practices occur during the 10 years.) a. The period prevalence rate will decrease b. The apparent 5-year survival will increase c. The age-adjusted mortality rate will decrease It generally differs from observes survival by a constant amount regardless of age None of the above
B
A new screening program was instituted in a certain country. The program used a screening test that is effective in detecting cancer Z at an early stage. Assume that there is no effective treatment for this type of cancer and therefore that the program results in no change in the usual course of the disease. Assume also that the rates noted are calculated from all known cases of cancer Z and that there were no changes in the quality of death certification of this disease. What will happen to the apparent case-fatality for cancer Z in the country during the first year of this program? a. Case-fatality will increase b. Case-fatality will decrease c. Case-fatality will remain constant
B
Choose the best study design from the list below for each of the following research questions. Each study design can only be used once. a. Ecologic study b. Cross-sectional study c. Case-control study d. Prospective cohort e. Randomized trial _____ An investigator wishes to determine if the prevalence of syphilis is higher among men than women.
B
In a randomized trial, a planned crossover design: a. Eliminates the problem of a possible order effect b. Must take into account the problem of possible residual effects of the first therapy c. Requires stratified randomization d. Eliminates the need for monitoring compliance and noncompliance e. Enhances the generalizability of the results of the study
B
In many studies examining the association between estrogens and endometrial cancer of the uterus, a one-sided significance test was used. The underlying assumption justifying a one-sided rather than a two-sided test is: a. The distribution of the proportion exposed followed a "normal" pattern b. The expectation before doing the study was that estrogens cause endometrial cancer of the uterus c. The pattern of association could be expressed by a straight-line function d. Type II error was the most important potential error to avoid e. Only one control group was being used
B
The best index (indices) for concluding that an early detection program for breast cancer truly improves the natural history of disease, 15 years after its initiation, would be: a. A smaller proportionate mortality for breast cancer 15 years after initiation of the early detection program compared to the proportionate mortality prior to its initiation b. Improved long-term survival rates for breast cancer patients (adjusted for lead time) c. A decrease in incidence of breast cancer d. A decrease in the prevalence of breast cancer e. None of the above
B
Two pediatricians want to investigate a new laboratory test that identifies streptococcal infections. Dr. Kidd uses the standard culture test, which has a sensitivity of 90% and a specificity of 96%. Dr. Childs uses the new test, which is 96% sensitive and 96% specific. If 200 patients undergo culture with both tests, which of the following is correct? a. Dr. Kidd will correctly identify more people with streptococcal infection than Dr. Childs b. Dr. Kidd will correctly identify fewer people with streptococcal infection than Dr. Childs c. Dr. Kidd will correctly identify more people without streptococcal infection than Dr. Childs d. The prevalence of streptococcal infection is needed to determine which pediatrician will correctly identify the larger number of people with the disease
B
A new screening program was instituted in a certain country. The program used a screening test that is effective in detecting cancer Z at an early stage. Assume that there is no effective treatment for this type of cancer and therefore that the program results in no change in the usual course of the disease. Assume also that the rates noted are calculated from all known cases of cancer Z and that there were no changes in the quality of death certification of this disease. What will happen to the apparent mortality rate from cancer Z in the country as a result of the program? a. Mortality rate will increase b. Mortality rate will decrease c. Mortality rate will remain constant
C
All of the following are potential benefits of a randomized clinical trial, except: a. The likelihood that the study groups will be comparable is increased b. Self-selection for a particular treatment is eliminated c. The external validity of the study is increased d. Assignment of the next subject cannot be predicted e. The therapy that a subject receives is not influenced by either conscious or subconscious bias of the investigator
C
Choose the best study design from the list below for each of the following research questions. Each study design can only be used once. a. Ecologic study b. Cross-sectional study c. Case-control study d. Prospective cohort e. Randomized trial _____ A researcher believes that a rare disease may be associated with use of a common lawn fertilizer.
C
In general, screening should be undertaken for diseases with the following feature(s): a. Diseases with a low prevalence in identifiable subgroups of the population b. Diseases for which case-fatality is low c. Diseases with a natural history that can be altered by medical intervention d. Diseases that are readily diagnosed and for which treatment efficacy has been shown to be equivocal in evidence from a number of clinical trials e. None of the above
C
The purpose of a double blind or double masked study is to: a. Achieve comparability of treated and untreated subjects b. Reduce the effects of sampling variation c. Avoid observer and subject bias d. Avoid observer bias and sampling variation e. Avoid subject bias and sampling variation
C
Which of the following is a good index of the severity of a short-term, acute disease? a. Cause-specific death rate b. 5-year survival c. Case-fatality d. Standardized mortality ratio e. None of the above
C
Which of the following is not a possible outcome measure that could be used as an indicator of the benefit of screen- ing programs aimed at early detection of disease? a. Reduction of case-fatality in screened individuals b. Reduction of mortality in the population screened c. Reduction of incidence in the population screened d. Reduction of complications e. Improvement in the quality of life in screened individuals
C
Which of the following statements about relative survival is true? a. It refers to survival of first-degree relatives b. It is generally closer to observed survival in elderly populations c. It is generally closer to observed survival in young populations d. It generally differs from observed survival by a constant amount, regardless of age e. None of the above
C
A screening test is used in the same way in two similar populations, but the proportion of false-positive results among those who test positive in population A is lower than that among those who test positive in population B. What is the likely explanation for this finding? a. It is impossible to determine what caused the difference b. The specificity of the test is lower in population A c. The prevalence of disease is lower in population A d. The prevalence of disease is higher in population A e. The specificity of the test is higher in population A
D
An advertisement in a medical journal stated that "2,000 subjects with sore throats were treated with our new medicine. Within 4 days, 94% were asymptomatic." The advertisement claims that the medicine was effective. Based on the evidence given above, the claim: Is correct May be incorrect because the conclusion is not based on a rate May be incorrect because of failure to recognize a long term cohort phenomenon May be incorrect because no test of statistical significance was used May be incorrect because no control of comparison group was involved
E
Choose the best study design from the list below for each of the following research questions. Each study design can only be used once. a. Ecologic study b. Cross-sectional study c. Case-control study d. Prospective cohort e. Randomized trial _____ Health officials in Baltimore City believe that a smoking cessation program in combination with nicotine patches will be more effective than a cessation program alone.
E
The major purpose of random assignment in a clinical trial is to: A. Help ensure that study subjects are representative of the general population b. Facilitate double blinding (masking) c. Facilitate the measurement of outcome variables d. Ensure that the study groups have comparable baseline characteristics e. Reduce selection bias in the allocation of treatment
E
