MATH 408 Midterm: MATH 408 USC M1 408 Fall 17 sol
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Instructor s. lototsky (kap 248d; x0 2389; lototsky@usc. edu) Instructions: no books or notes of any kind, turn o cell phones, you should have (and use!) a calculator and three distribution tables: nor- mal, t, and 2. You are welcome to use statistical functions in your calculator instead of the tables: answer all questions and clearly indicate your answers, each problem is worth 10 points, show your work! Points might be taken o for a correct answer with no explanations. Given the set of numbers 39, 54, 61, 72, 59, 49, and assuming that this is a sample from a normal population, construct the 90% con dence interval for the standard deviation. The answer is [7. 55, 23. 48] or something around that. The key numbers are s2 n = 126. 2(6), 5 = 6 1 degrees of freedom, and the quantiles 1. 145 and 11. 071 for 2. The key fact is that (n 1)s2 n/ 2 has 2 n 1 distribution.
