Sahmoun's Review

What are different means of measuring medication compliance?

1. Pill count (check the # of pills in the box) 2. Measuring a biomarker in blood or urine 3. Questioning clinic personnel

Arrange the following study designs, from the weakest (top) to the strongest (bottom), according to their strength of evidence in determining cause-effect relationship Cohort studies; Randomized controlled trials; Case-reports; Cross-sectional studies; Case-series; Case-control studies

1. case-report 2. case-series 3. cross-sectional 4. case-control 5. cohort study 6. randomized controlled trials

How do we control for the effects of confounding?

1. randomization 2. stratification 3. matching 4. adjustment using multivariable analysis 5. restriction

3 ways that masking can occur

1. subjects (single blind) 2. investigators (double) 3. evaluation team (triple)

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: A. Type I error (α error) B. Type II error (β error) C. 1 - α D. 1 - β E. None of the above

A. Type I error (α error)

In a prospective study, the occurrence of transitional cell carcinoma of the bladder was recorded for smokers and nonsmokers. The difference in incidence between smokers and nonsmokers was reported to be significant at the p < 0.05 level. The most appropriate statement that can be made about this study is that A. the null hypothesis may be rejected even though the results could have occurred purely by chance a maximum of 5% of the time B. a significant difference in the incidence between smokers and nonsmokers may occur 5% of the time or less C. the null hypothesis may be accepted because there is a difference in the incidence rates between smokers and nonsmokers only 5% of the time D. the alternate hypothesis may be rejected because the null hypothesis is true up to 5% of the time E. a causal relationship between smoking and the incidence of transitional-cell carcinoma of the bladder may be established at a significance level of 0.05

A. the null hypothesis may be rejected even though the results could have occurred purely by chance a maximum of 5% of the time

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. Must take into account the problem of possible residual effects of the first therapy

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 expectation before doing the study was that estrogens cause endometrial cancer of the uterus

Exposure & disease measured simultaneously. Survey data use an option (prevalence)

C-sectional

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. Avoid observer and subject bias

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. The external validity of the study is increased

The power of a statistical test can be determined by using the formula A. 1 - H0 B. 1 - HA C. 1 - α D. 1 - β E. H0 - HA

D. 1 - β

Following a large group of cigarette smokers for a period of 10 years to determine the occurrence of chronic obstructive pulmonary disease, coronary heart disease, and various forms of lung cancer would be an example of a A. randomized clinical trial B. cross-sectional study C. prevalence study D. cohort study E. case-control study

D. cohort study

Statistical methods are used in medical research because they A. provide values for results that are dependent upon chance B. provide conclusions about cause and effect C. provide controls for variables that were absent in the study design D. provide assurance of the significance of the findings E. provide controls for some of the more common sources of experimental error

D. provide assurance of the significance of the findings

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: A. Is correct B. May be incorrect because the conclusion is not based on a rate C. May be incorrect because of failure to recognize a long-term cohort phenomenon D. May be incorrect because no test of statistical significance was used E. May be incorrect because no control or comparison group was involved

E. May be incorrect because no control or comparison group was involved

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 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. Reduce selection bias in the allocation of treatment

What does randomization do for you?

Eliminate selection bias; increase comparability groups; valid tests

refers to any concept or strategy that is derived from or informed by objective evidence—most commonly, scientific research

Evidence-based

T/F Bias can be prevented or minimized by taking a larger sample

FALSE

T/F Case-Control Studies are prospective in that they follow the cases and controls over time and observe what occurs

FALSE

What does stratified randomization do for you?

Guarantees comparability of the groups on important prognostic factors (confounders)

T/F Bias can occur in observational studies

TRUE

T/F Bias could be due to problems in the selection of the population to be studied

TRUE

T/F Bias is an error in design or execution of a study that produces results that are consistently distorted in one direction and lead to an incorrect assessment of the association between the factor and the disease under study

TRUE

T/F Case-reports are not considered evidence-based even though the authors have studied the case in great depth

TRUE

T/F In a cohort study, an exposure is assessed and then participants are followed prospectively to observe whether they develop the outcome

TRUE

3 common confounders

age, gender, race

type 1 error

alpha; when the null hypothesis is rejected and there is no difference

Cohort Studies generally look at which of the following? a) Determining the sensitivity and specificity of diagnostic methods b) Identifying risk factors associated with a disease c) Variations among the clinical manifestations of patients with a disease d) The impact of blinding or masking a study population e) a, c, and d

b) Identifying risk factors associated with a disease

What is the purpose of the control group in a case-control study? a) To provide information on the disease distribution in the population that gave rise to the cases b) To provide information on the exposure distribution in the population that gave rise to the cases c) a and b

b) To provide information on the exposure distribution in the population that gave rise to the cases

When are Case-reports most useful? a) When you encounter common cases and need more information b) When new symptoms or outcomes are unidentified c) When developing practice guidelines d) When the population being studied is very large e) All of the above

b) When new symptoms or outcomes are unidentified

In a study begun in 2015, a group of 5,000 adults in Montana were asked about alcohol consumption. The occurrence of cases of cancer between 2019 and 2020 will be studied in this group. This is an example of: a. A cross-sectional study b. A prospective cohort study c. A retrospective cohort study d. A clinical trial e. A case-control study

b. A prospective cohort study

A study is designed to evaluate the feasibility of acupuncture in children with chronic headaches. Sixty children with chronic headaches are recruited for the study. In addition to their usual therapy, all children are treated with acupuncture three times a week for 2 months. Which of the following best describes this study design? a. Case-control b. Case-series c. Crossover d. Cross-sectional e. Historical cohort f. Randomized clinical trial

b. Case-series

type 2 error

beta; fail to reject the null when there is a difference

what is the purpose of masking?

bias reduction

In a cohort study, the advantage of starting by selecting a defined population for study before any of its members become exposed, rather than starting by selecting exposed and non-exposed individuals, is that: a. The study can be completed more rapidly b. A number of outcomes can be studied simultaneously c. A number of exposures can be studied simultaneously d. The study will cost less to carry out e. a and d

c. A number of exposures can be studied simultaneously

A Case-Control study is characterized by all of the following except: a. It is relatively inexpensive compared with most other epidemiologic study designs b. Patients with the disease (cases) are compared with persons without the disease (controls) c. Incidence rates may be computed directly d. Assessment of past exposure may be biased e. Definition of cases may be difficult

c. Incidence rates may be computed directly

Which of the following is a Case-Control study? a. Study of past mortality or morbidity trends to permit estimates of the occurrence of disease in the future b. Analysis of previous research in different places and under different circumstances to permit the establishment of hypotheses based on cumulative knowledge of all known factors c. Obtaining histories and other information from a group of known cases and from a comparison group to determine the relative frequency of a characteristic or exposure under study d. Study of the incidence of cancer in men who have quit smoking e. Both a and c

c. Obtaining histories and other information from a group of known cases and from a comparison group to determine the relative frequency of a characteristic or exposure under study

Retrospective cohort studies are characterized by all of the following except: a. The study groups are exposed and non-exposed b. Incidence rates may be computed c. The required sample size is smaller than that needed for a prospective cohort study d. The required sample size is similar to that needed for a prospective cohort study e. They are useful for rare exposures

c. The required sample size is smaller than that needed for a prospective cohort study

Starts with patients who have a disease (cases) and patients who do not have the disease (controls), and looks back to compare how frequently the exposure is present in each group

case-control

A group of individuals with and without an exposure is followed and subsequent disease status is determined

cohort

a variable that is associated with the exposure and, independent of that exposure, is a risk factor for the disease

confounder

Involves the possibility that the observed association is due, totally or in part, to the effects of differences between the study groups other than the exposure under study that could affect their risk of developing the outcome of interest

confounding

The physical examination records of the entire incoming freshman class of 1945 at the University of North Dakota were examined in 1987 to see if their recorded height and weight at the time of admission to the university was related to the development of coronary heart disease by 1996. This is an example of: a. A cross-sectional study b. A case-control study c. A concurrent cohort study d. A retrospective cohort study e. An experimental study

d. A retrospective cohort study

To investigate whether there is an association between smoking and type 2 diabetes, a researcher asked a group of people if they are currently smoking and if they had type 2 diabetes. In answering "yes" to smoking, the individual was asked how many packs/day. What kind of study design is this? a. Cohort study b. Ecological study c. Randomized control study d. Cross-sectional study e. Case report

d. Cross-sectional study

In cohort studies of the role of a suspected factor in the etiology of a disease, it is essential that: a. There be equal numbers of persons in both study groups b. At the beginning of the study, those with the disease and those without the disease have equal risks of having the factor c. The study group with the factor and the study group without the factor be representative of the general population d. The exposed and non-exposed groups under study be as similar as possible with regard to possible confounding factors e. Both b and c

d. The exposed and non-exposed groups under study be as similar as possible with regard to possible confounding factors

Which of the following is an advantage of Case-Control Studies? a) They can simultaneously look at multiple risk factors b) They are useful to initially establish an association between a risk factor and a disease c) They take less time to complete because the condition or disease has already occurred d) b and c only e) a, b, and c

e) a, b, and c

In a study of a disease in which all cases that developed were ascertained, if the relative risk for the association between a factor and the disease is equal to or less than 1.0 , then: a. There is no association between the factor and the disease b. The factor protects against development of the disease c. Either matching or randomization has been unsuccessful d. The comparison group used was unsuitable, and a valid comparison is not possible e. There is either no association or a negative association between the factor and the disease

e. There is either no association or a negative association between the factor and the disease

Done at a group level (subject to ecological fallacy)

ecological

an approach to medical practice intended to optimize decision-making by emphasizing the use of evidence from well-designed and well-conducted research

evidence-based medicine

drop outs vs drop ins

outs: Patient in treatment group stops taking therapy ins: Patient in control group starts taking experimental therapy

in a crossover clinical trial, who serves as the controls?

participants serve as their own controls Participant receives treatment A, washout treatment A, receives treatment B, washout treatment B, etc-- assumes no carryover effect of previous treatment

In a ___ study, baseline information is collected from all subjects in the same way using exactly the same questions and data collection methods for all subjects ; subjects are following "longitudinally/future"; i.e. over a period of time, usually for years, to determine if and when they develop the disease; its a pre-planned study

prospective study

Random assignments of participants into an interventional group OR a control group (experimental)

randomized controlled trials

occurs when asked to recall events (individuals in one group are more likely than those in another group to remember the event)

recall bias

___ studies are conceived after some people have already developed the outcome(s) of interest. The investigators jump back in time to identify a cohort of individuals at a point in time before they have developed the outcomes of interest, and they try to establish their exposure status at that point in time. They then determine whether the subject subsequently developed the outcome of interest (became diseased or not)

retrospective

occurs whenever the manner of selection of study participants creates a deviation between the measurement of the association in the study and the real magnitude of the association between factor and disease in the population

selection bias