Community Medicine Practice

20 learning units • 10 questions per unit • 200 explained questions

Module 03 — Study Designs & Causal Reasoning

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Question 01 • Single best answer

A survey measures smoking and breathlessness on the same day. What major causal limitation remains?

A. Temporal order may be unclear B. Prevalence can never be measured C. Every participant must be randomized D. All selection bias is eliminated

Question 02 • Single best answer

Investigators recruit people with lung cancer and controls, then compare past smoking. Which design is this?

A. Case-control B. Randomized trial C. Prospective cohort by exposure D. Pure laboratory experiment

Question 03 • Single best answer

Workers are grouped by dust exposure and followed for new disease. Which design fits?

A. Case series only B. Ecological correlation only C. Case-control sampling D. Cohort

Question 04 • Single best answer

What should controls in a case-control study represent?

A. Only people who can never develop disease B. A group selected for unusually low exposure C. Any convenient group regardless of source D. The source population that produced the cases

Question 05 • Single best answer

What does allocation concealment primarily prevent?

A. Every loss to follow-up B. All post-treatment measurement error C. Predicting assignment during recruitment D. Variation in disease biology

Question 06 • Single best answer

What does intention-to-treat analysis generally preserve?

A. Only perfect adherers in each arm B. Removal of every adverse outcome C. Guaranteed absence of missing data D. Comparison according to randomized assignment

Question 07 • Single best answer

Differential recall of past exposure by cases is an example of what?

A. Information bias B. Perfect blinding C. Random sampling D. Effect modification by definition

Question 08 • Single best answer

An exposure effect differs meaningfully by age group. What might this represent?

A. Necessarily fraudulent data B. Guaranteed selection bias C. Proof that all subgroup findings are false D. Effect modification

Question 09 • Single best answer

Higher district income correlates with a health outcome. What inference is unsafe without individual data?

A. A group-level association was observed B. Districts were the units compared C. Every higher-income individual has the same relationship D. Further research may be useful

Question 10 • Single best answer

What does a meta-analysis of biased studies fail to guarantee?

A. An unbiased causal estimate B. A numerical summary C. A stated pooling method D. More included observations