STAT151 Chapter 11: Stats Chapter 11 Experiments and Observational Studies

• School: University of Alberta
• Department: Statistics
• Course: STAT151
• Professor: Alireza Simchi

Document Summary

Observational studies: resear(cid:272)hers do(cid:374)"t assig(cid:374) (cid:272)hoi(cid:272)es, the(cid:455) just o(cid:271)ser(cid:448)e the(cid:373, good for identifying trends and possible relationships. Retrospective study: researchers first identified subjects then collected data from the past, observational studies that try to discover variables related to rare outcomes, based on historical data can have errors. Identifying subjects in advance and collecting data as events unfold. A variable whose levels are controlled by the experimenter. Experiments attempt to discover the effects that differences in factor levels may have on the responses of the experimental units: at least one response variable to measure response variable. A variable whose values are compared across different treatments. In a randomized experiment, large response differences can be attributed to the effect of differences in treatment level. Experimental units: the individuals on whom or which we experiment. Levels of the factor: the specific values that the experimenter chooses for a factor. Ex. sleep for 4, 6, or 8 hours.