Question

1. A case-control study was performed to determine whether head injury was associated with an increased risk of brain tumors in children. 200 cases with brain cancer were identified from the state cancer registry and 200 controls were recruited from the same neighborhoods where the cases lived. The mothers of the children completed a questionnaire that asked them to describe their child's past history of head injury. The investigators found that the mothers of the children with brain tumors reported a past head injury for 70 of the cases while a past history of head injury was reported in 30 of the controls. What type of bias was likely to have influenced the findings of this study?

		Length bias
		Recall bias
		Surveillance, diagnostic, or referral bias
		Interviewer bias

2-After investigators calculate a measure of association (RR for cohort studies and OR for case-control studies), they must evaluate whether or not the observed result is true.

		True
		False

3-Bias in epidemiologic studies means that the investigator is "prejudiced".

		True
		False

4-Control selection bias occurs in a case-control study when cases remember or report their exposures differently (more or less accurately) from controls.

		True
		False

Answer 1

1-

Recall Bias

This type of a bias is termed as the 'Recall Bias'. It happens when responders of a survey try to recall their past events, but they don’t usually are able to recall a complete or precise picture of what had happened in the past . This happens due to the fact that our brains are in a continous process of rewriting memories, clouding them with cross-thoughts.

2-

False

Evaluation of whether or not the observed result is true won't happen in an actual study.

3-

False

The bias in epidemiologic studies does not usually takes place due to the investigater being "prejudiced", but rather due to ignorance or unavoidable decisions made during the duration of the study.

4-

True

A control selection bias occurs in a case-control study, when when cases remember or report their exposures differently (more or less accurately) from controls i.e, the subjects for the "control" group won't truly represent the population that had produced the cases significantly.