Exam 2

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Question #1

To address at least partially the problem of confounding in a case-control study, investigators usually select …(choose one best answer),,,,

A simultaneous non-randomized controls

B matched controls

C historical controls

D random controls

E non-stratified controls

Question #2

In a cross-sectional study of hypertension and obesity with 1,200 subjects, 50 of 200 obese subjects were currently hypertensive, as compared to 60 of 1,000 non-obese subjects. What is the appropriate measure for the association between obesity and hypertension that can be calculated in this study? (choose one best answer)

A Prevalence odds ratio

B Cannot be calculated

C Rate ratio

D Risk ratio

Question #3

In a matched-pairs case-control study, you derive the odds ratio by dividing the number of exposed cases and unexposed controls by the number of unexposed cases and unexposed controls. (mark as True or False)

A TRUE

B FALSE

Question #4

The power of an experimental study comparing two treatment groups is 90%. Which of the following statements is true? (choose one best answer)

A The probability of making a type II error is 10%.

B The probability of correctly concluding that two treatments did not differ is 90%.

C The p-value of the study is 0.1

D probability of concluding that therapies differ when they do not differ in reality is 10%.

E The probability of making a type I error is 10%.

Question #5

A researcher wants to study an association between childhood leukemia and exposure to electro-magnetic fields. Childhood leukemia (children aged from 0 to 21) has an incidence of 3-4 cases per 100,0000 children. What would be the most inappropriate study design for this study? (choose one best answer)

A Cohort study

B Case-control study

C Ecological study

D Cross-sectional

E Randomized trial

Question #6

Factor A and factor B are risk factors for disease D. The relative risk of disease D comparing those exposed to factor A to those unexposed to factor A is 4. The RR of disease comparing those exposed to factor B to those unexposed to factor B is 2. The observed RR for those exposed to both factors compared to those unexposed to both factors is 11. The additive effect of interaction between factor A and factors B is RR=8. Based on the these finding the conclusion would be that there is a synergetic (positive) interaction between factor A and factor B in the development of disease D. (mark as True or False)

A TRUE

B FALSE

Question #7

Ecological study design is often used for assessing causal relationships between an exposure and a disease of interest. (mark as True or False)

A TRUE

B FALSE

Question #8

During one-month period a study gathered information from all patients at a Hospital Y about their alcohol drinking habits and then identified those who had injuries at the time of the study in order to assess the relationship between alcohol drinking and injuries. The researchers found that percentage of injuries was higher among alcohol drinkers than in those who did not drink alcohol. What was the study design in the study? (choose one best answer)

A Ecological study

B Case-control study

C Cohort study

D Cross-sectional

E Randomized trial

Question #9

Causal relationships in the majority of chronic diseases are more accurately represented by the following type of causal relationships: (choose one best answer)

A Necessary, but no Sufficient

B Not necessary, but Sufficient

C Neither Necessary, Not Sufficient

D Necessary and Sufficient

Question #10

The mortality from adenocarcinoma of lungs in those who never smoked is 3.4 per 100,000 PY, the mortality in those who smoked 1-2 packs/day is 143.9 per 100,000 PY. This is an example of … (choose one best answer):

A Specificity of the association

B Biological plausibility

C Strength of association

D Dose-response

Question #11

A researcher want to study a relationship between chronic stress and high blood pressure. The researcher should not adjust for smoking status or stratify on it during analysis. (mark as True or False)

A TRUE

B FALSE

Question #12

A factor is considered a confounder if that factor is a known risk factor for a disease of interest and if that factor is associated with an exposure of interest, but it is not a result of it. (mark as True or False)

A TRUE

B FALSE

Question #13

The major criteria in determining causality of a detected association are … : (choose one best answer)

A Specificity of the association, Temporal relationships, Biological plausibility

B Temporal relationships, Replication of findings, Consideration of alternative explanations

C Specificity of the association, Dose-response relationships, Cessation of exposure

D Dose-response relationships, Replication of findings, Strength of association

Question #14

The best method to address confounding issue is … (choose one best answer)

A Adjustment in the model

B Stratification

C Individual or group matching

D All of the methods listed

Question #15

Confounding is a problem that may occur only in observational studies, but not in randomized trials. (mark as True or False)

A TRUE

B FALSE

Question #16

A researcher requested a personal interview with every woman aged 17-22, who attended the student health services at USC between March 1 and May 1, 2006. Among the 75% who agreed to participate, the association between amount of sexual activity within the past 2 months and presence of urinary tract infection at the time of interview was assessed. What was the study design in the study? (choose one best answer)

A Randomized trial

B Ecological study

C Cross-sectional study

D Cohort study

E Case-control study

Question #17

In a retrospective cohort study, the investigator is convinced of the hypothesis and searches past records more carefully for exposure among persons who became cases versus those who did not. This is an example of… (choose one best answer)

A analytic bias

B outcome misclassification bias

C loss to follow-up bias

D information bias

E non-response bias

Question #18

One of the major problems causing biased (faulty) results in observational studies is confounding. (mark as True or False)

A TRUE

B FALSE

Question #19

Of the following, which bias is generally more of a problem in prospective cohort studies than in case-control studies: (choose one best answer)

A confounding bias

B biases from loss-to-follow-up

C analytic bias

D recall bias

Question #20

An investigator is interested in the relationship between birth weight and childhood asthma. He plans to identify children with asthma who were treated in Children’s Hospital in Los Angeles during five years starting from January 2010, then he plans to obtain information about their birth weight through birth registiry of California, and assign children either low birth weight or normal birth weight. This study is an example of: (choose one best answer)

A Cohort experiment

B Prospective cohort study

C Prospective cohort study

D Case-control study

Question #21

An investigator wants to perform an experimental study on the effectiveness of a new therapy (Therapy A), compared to the current therapy (Therapy B) for gastric ulcer. The study sample is 400 patients aged 18 years or older who are admitted to a Medical Center with a diagnosis of gastric ulcer as the main reason for admission. It was also decided that, starting August 1, 2009, any eligible patient will be invited to participate until a total of 400 eligible patients is obtained. Which of the following treatment assignment schemes cannot be used so that the study is properly called a randomized controlled trial? (choose one best answer)

A Any assignment scheme that makes it impossible to predict what is the therapy that the next patient will receive

B Tossing a coin 400 times

C Using random number table

D Any eligible patient admitted on an even-numbered day will be assigned to Therapy A; any eligible patient admitted on an odd-numbered day will be assigned to Therapy B.

Question #22

The physical examination of the entire undergraduate students of class 1965 at CSUN were examined in 2005 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 2015. This is an example of … (choose one best answer).

A Cross-sectional study

B Randomized trial

C Prospective cohort study

D Retrospective cohort study

E Case-control study

Question #23

Assume you are planning an experiment and are particularly concerned that patients may switch their treatment group. A good solution would be to do… (choose one best answer).

A stratified randomization

B cross-over randomization

C factorial randomization

D outcome randomization

E masking of group assignments

Question #24

A randomized trial was conducted of smoking-cessation programs. One group received counseling alone (C), the second group received nicotine-laced gum (N), the third group received counseling and nicotine-laced gum (CN), the last group did not receive neither counseling nor nicotime-laced gun, only printed brouchure (B). This is an example of… (choose one best answer):

A a generalization design

B a factorial design

C a compliance design

D a cross-over design

Question #25

Randomization ensures comparability of patients by all factors and characteristics in the new and existing therapy groups. (mark as True or False)

A TRUE

B FALSE

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