Statistical Sciences 1024A/B Lecture Notes - Lecture 8: Call Screening, Quebec Sovereignty Movement, Stratified Sampling
20 Apr 2016
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An observational study observes individuals and measures variables of interest but does not attempt to. A designed experiment (or simply experiment) deliberately imposes some treatment on individuals in influence the responses order to observe their responses. Divide the experimental units into a number of different groups corresponding to the number of treatments. Measure the units to see if there are differences between the treatments. 1% of people who contracted the polio virus suffered from the paralytic form of the disease. A vaccine was developed by jonas salk; tested in 1954. In the test, 440,000 children received the vaccine and 210,000 the placebo. Confounding variables are a common problem with observational studies. Two variables (explanatory or lurking) are confounded when their effects on the response variable cannot be distinguished or isolated from one another. Suppose we want to compare pay levels between two types of jobs: inside workers and outside workers. The inside workers evaluated turn out to be all female.
