Question

9. Bias is less likely to invalidate a cohort study used to assess the risk of disease due to an exposure because: A. The presence or absence of exposure is determined prior to disease occurrence B. The sample sizes in cohort studies are large C. Disease status is always known at the start of the study D. Incident cases of the disease are distinguished from prevalent cases in the analyses E. Analyses are based on a comparison of the proportion of prevalent cases of disease in each group, rather than simply the absolute number of cases in each group 10. Match the following choices (1 – 4) that best fits (i.e., most efficient and logical) each of the following scenarios (A-F) 1. Case Control Study 2. Retrospective Cohort Study 3. Prospective Cohort Study 4. None of these selections Identifying the cause of a disease. B. __Identifying the long term effects of a rare exposure. Studying the health effects of an exposure for which information is difficult and expensive to obtain. D. Identifying the causes of a new disease about which little is known. Identifying the short term health effects of a new exposure about which little is known. Identifying the causes of a disease with a long latent period.

Answer 1

9) Bias is less likely to invalidate a cohort study used to assess the risk of the disease due to an exposure because of the options A and B

Option A- The presence or absence of an exposure is determined prior to disease occurence (because of this, we can calculate the rate of disease in exposed and non exposed individuals example- incidence and relative risk).

Option B- The sample size in cohort studies are large (large sample size provides more accurate mean values, more relevance).

10)

1- D

Case control studies identifies the cause of new disease about which little is known.

2 - F

Retrospective cohort studies identifies the cause of a disease with a long latent period.

3 - C

Prospective cohort studies study the health effects of an exposure for which information is difficult and expensive to obtain.

4 - A

None of these selections identify the cause of a disease (that means these studies aid in identifying the causes for a disease but not the exact cause of a particular disease).