# hw6 - year We take a sample of 30 students on campus...

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Homework 6 Due in class on April 11 th . 1) We have a sample with a mean of 10, variance of 9 and a sample size of 100. a) Build a 90% conﬁdence interval. b) Build a 95% conﬁdence interval. c) Build a 99% conﬁdence interval. d) List to CI’s from widest to narrowest. Very brieﬂy explain why the CI’s are in this order. 2) We draw a sample from a population with unknown mean and variance. That sample has a variance of 25, a mean of 8 and a sample size of 36. a) Build a 95% conﬁdence interval for μ . b) We discover that the population variance is 81. Recalculate the 95% conﬁ- dence interval taking that information into account. BRIEFLY explain why the two CI’s are diﬀerent. 3) We are interested in how much money work study students earn in a school
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Unformatted text preview: year. We take a sample of 30 students on campus receiving work study. Their average income is \$3800 a year with a variance of \$1200. Does the average work study student earn more than \$4000 per year? Build a 95% conﬁdence interval to answer this question. 4) Work problem 11.18 in the text. In addition to the 95% conﬁdence interval build a 90% and 99% CI. Interpret these intervals. What can you say about the diﬀerences in the two populations. 5) We calculate the average weight of 25 high school seniors in Boulder is 155 pounds. The sample variance is 200. Find the p-values and test the hypothesis: H O : μ = 170 H A : μ < 170 at the 0.1, 0.05 and 0.01 level. 1...
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## This note was uploaded on 04/08/2008 for the course ECON 3070 taught by Professor Loh,joyce during the Spring '07 term at Colorado.

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