HSCI 330 Lecture 5: week 5 note

• School: Simon Fraser University
• Department: Health Sciences
• Course: HSCI 330
• Professor: Hasina Samji

Document Summary

**selection bias systematic error between the study and source population: & information bias & confounding. Random error between sample and study population. In case-control studies, the primary source of selection bias is: the manner in which cases, controls, or both are selected and, the extent to which exposure history influence such selection. Q8. 1: the odds ratio is overestimated, so a has a weaker association with b than actually observed; the bias would be away from the null (chapter 7) Q8. 1 cont"d: a suspected association may have resulted in preferential diagnosis of b among known users of a when compared with nonusers. The proportion exposed among diagnosed cases selected for study is likely to be larger than the proportion exposed among all cases in the source population. In cohort studies and clinical trials, the primary sources of selection bias are: loss-to-follow-up, withdrawal from the study, non-response. Q8. 2 new cancer regimen versus standard regimen .