STATS 305 Midterm: STAT 305a Exam Fall 2015
31 Jan 2019
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No aids allowed: no texts notes, computers, cell phones, or calculators. The questions below require fairly short answers and are of equal value. No one is expected to answer all of the questions. but everyone is encouraged to try them. All answers should be written in the space provided. Since you don"t have a computer or calculator, it"s ok to stop short of the nal numerical answer. Eg you can express an answer as (1. 8) (or pnorm(1. 8)), or (1 . 01)20: suppose that an investigator nds that the risk of breast cancer in an observational study is correlated strongly with dietary fat intake. He throws total consumption of saturated fats into the model and nds that the parameter estimate is signi cant. However, when he adds total con- sumption of unsaturated fats into the regression as well, its parameter estimate is not signi cant. He then concludes that saturated fats are dangerous, but not unsaturated fats.
