Epi Exam 3 Questions And Answers
Other names for:
1. Case-control study
2. Cohort study
3. Prospective cohort study
4. Retrospective cohort
5. Randomized trial
6. Cross-sectional - ANSWER 1. Retrospective study
2. Longitudinal study, prospective study
3. Concurrent cohort/concurrent prospective
4. Historical cohort/nonconcurrent prospective
5. Experimental study
6. Prevelence Survey
Nature of Case-control studies - ANSWER 1. Persons with and without disease selected;
proportions of each group who have been exposed are determined
2. Originated as response to teh shift from acute to chronic diseases as major public
health problem
3. Most frequently undertaken type of observational analytic epidemiologic study
4. Affected by bias more than other study designs, so each must be evaluated
individually
5. Compares one case group to one or more control groups
Odds Ratio Defn - ANSWER An estimate of the relative risk calculated as the ratio of the
odds of exposure among cases versus control
,Odds Ratio formula - ANSWER OR = ad/bc
a = no. of exposed cases
b = no. of exposed controls
c = no. of nonexposed cases
d = no. of nonexposed controls
Meaning of different values of OR - ANSWER A. OR = 1.0 indicates odds of exposure are
identical in case and control groups (no association)
B. OR > 1.0: increased odds of exposure among cases as compared to controls (harmful
exposure effect)
C. OR < 1.0: decreased odds of exposure among cases as compared to controls
(protective exposure effect)
The odds ratio is the comparison of
A. Two incidence rates
B. Two prevalence rates
C. Both
D. Neither - ANSWER D.
Controls are needed in a case-control study because
A. They are matched to teh cases for suspected etiologic factors
B. They increase the sample size, so that statistical significance may be achieved
C. They may be followed to determine if they develop the disease in question
D. They provide a comparable estimate of the frequency of exposure in the absence of
time
E. They reduce bias - ANSWER D.
An unmatched case-control study is conducted evaluating folic acid nutrition and
congenital defects. Maternal folate deficiency was found in 15 of 100 mothers of cases
, and 10 of 200 mothers of controls. What is the odds of exposure (folate deficiency)
among mothers of cases
A. 10/200
B. 10/190
C. 15/100
D. 15/85
E. 15/10 - ANSWER D.
Rare disease assumption- ANSWER When the disease is rare the total number exposed
can be approximated by the number of exposed controls and total unexposed by the
number of non-exposed controls
Attributable Risk - ANSWER Ie - Io
Can be calculated if incidence rates can be estimated among exposed and nonexposed
groups
The population-based breast cancer case-control data presented in the table below,
calculated the attributaale risk for being single
Marital Status | Cases | Controls | Total
Single | 20 | 20 | 40
Married | 80 | 180 | 260
Total | 100 | 200 | 300
A. 0 - 25%
B. 26 - 50%
C. 51 - 75%
D. 76 - 100%
E. Cannot be calculated from the data given - ANSWER E
From the population-based breast cancer case-control data below. The incidence rate
Other names for:
1. Case-control study
2. Cohort study
3. Prospective cohort study
4. Retrospective cohort
5. Randomized trial
6. Cross-sectional - ANSWER 1. Retrospective study
2. Longitudinal study, prospective study
3. Concurrent cohort/concurrent prospective
4. Historical cohort/nonconcurrent prospective
5. Experimental study
6. Prevelence Survey
Nature of Case-control studies - ANSWER 1. Persons with and without disease selected;
proportions of each group who have been exposed are determined
2. Originated as response to teh shift from acute to chronic diseases as major public
health problem
3. Most frequently undertaken type of observational analytic epidemiologic study
4. Affected by bias more than other study designs, so each must be evaluated
individually
5. Compares one case group to one or more control groups
Odds Ratio Defn - ANSWER An estimate of the relative risk calculated as the ratio of the
odds of exposure among cases versus control
,Odds Ratio formula - ANSWER OR = ad/bc
a = no. of exposed cases
b = no. of exposed controls
c = no. of nonexposed cases
d = no. of nonexposed controls
Meaning of different values of OR - ANSWER A. OR = 1.0 indicates odds of exposure are
identical in case and control groups (no association)
B. OR > 1.0: increased odds of exposure among cases as compared to controls (harmful
exposure effect)
C. OR < 1.0: decreased odds of exposure among cases as compared to controls
(protective exposure effect)
The odds ratio is the comparison of
A. Two incidence rates
B. Two prevalence rates
C. Both
D. Neither - ANSWER D.
Controls are needed in a case-control study because
A. They are matched to teh cases for suspected etiologic factors
B. They increase the sample size, so that statistical significance may be achieved
C. They may be followed to determine if they develop the disease in question
D. They provide a comparable estimate of the frequency of exposure in the absence of
time
E. They reduce bias - ANSWER D.
An unmatched case-control study is conducted evaluating folic acid nutrition and
congenital defects. Maternal folate deficiency was found in 15 of 100 mothers of cases
, and 10 of 200 mothers of controls. What is the odds of exposure (folate deficiency)
among mothers of cases
A. 10/200
B. 10/190
C. 15/100
D. 15/85
E. 15/10 - ANSWER D.
Rare disease assumption- ANSWER When the disease is rare the total number exposed
can be approximated by the number of exposed controls and total unexposed by the
number of non-exposed controls
Attributable Risk - ANSWER Ie - Io
Can be calculated if incidence rates can be estimated among exposed and nonexposed
groups
The population-based breast cancer case-control data presented in the table below,
calculated the attributaale risk for being single
Marital Status | Cases | Controls | Total
Single | 20 | 20 | 40
Married | 80 | 180 | 260
Total | 100 | 200 | 300
A. 0 - 25%
B. 26 - 50%
C. 51 - 75%
D. 76 - 100%
E. Cannot be calculated from the data given - ANSWER E
From the population-based breast cancer case-control data below. The incidence rate
