Notes 4b - Chapter 3- Producing Data: 3.2 Designing...

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Chapter 3- Producing Data: 3.2 Designing Experiments: Observation vs. Experiments: An observational study observes individuals and measures variables of interest but does not attempt to influence the responses. The purpose of an observational study is to describe some group or situation. An experiment , on the other hand, deliberately imposes some treatment on individuals in order to observe their responses. The purpose of an experiment is to study whether the treatment causes a change in the response. Experiment terminology: The treatment group is the group(s) of subjects who receive the treatment being tested. The control group is the group of subjects who do NOT receive the treatment. Example 1- Observational study: *Should women take hormones such as estrogen after menopause, when natural production of these hormones ends? In 1992, several major medical organizations said “Yes.” In particular, women who took hormones seemed to reduce their risk of a heart attack by 35% to 50%. The risks of taking hormones appeared small compared with the benefits. Example 2- Experimental study: In a study, women are assigned to take either hormone replacement or placebo pills (that look and taste the same as the hormone pills). The assignment is done by a coin toss, so that all kinds of women are equally likely to get either treatment. Example 3: Ask men and women to choose which features they consider essential in a health plan to see whether the required features differ across genders. Observational study of Experimental study? Example 4:
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Notes 4b - Chapter 3- Producing Data: 3.2 Designing...

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