EPID 301 Chapter Notes - Chapter 13: Time Point, Confidence Interval, Statistical Power

• School: Queen's University
• Department: Community Health and Epidemiology
• Course: EPID 301
• Professor: Helene Ouellette-Kuntz

Document Summary

In epidemiology, cohort studies assemble groups of subjects, often based on an exposure (not disease), and then compare outcomes in relation to this exposure over time. There are 2 types of cohort-study designs: prospective (looks forward in time; from the present to future) and retrospective (looks back in time; from the present to the past) Temporal direction, logical direction and study-design classification. Cohort studies differ in temporal direction, but they always have the same logical direction of inquiry. The logical direction in case-control studies is back ward: these studies start with an effect (cases have the disease) and then look for a cause (exposures) The logical direction in cohort studies is forward: they start with a possible cause (exposure) and then look for effects (disease) Since cross-sectional studies begin with a sample intended to represent a population at a point in time, they do not have direction to their logical inquiry. Cross-sectional studies have neither temporal nor logical direction.