- A case-control study was performed to determine whether headinjury was associated with an increased risk of brain tumors inchildren. 200 cases with brain cancer were identified from thestate cancer registry and 200 controls were recruited from the sameneighborhoods where the cases lived. The mothers of the childrencompleted a questionnaire that asked them to describe their child'spast history of head injury. The investigators found that themothers of the children with brain tumors reported a past headinjury for 70 of the cases while a past history of head injury wasreported in 30 of the controls. What type of bias was likely tohave 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 forcohort studies and OR for case-control studies), they must evaluatewhether or not the observed result is true.
3-Bias in epidemiologic studies means that the investigator is\"prejudiced\".
4-Control selection bias occurs in a case-control study whencases remember or report their exposures differently (more or lessaccurately) from controls.
