Si - week 13 worksheet

# Si - week 13 worksheet - MATH 218 SI Session(Fall 2008 Week...

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MATH 218 SI Session (Fall 2008) Week 13 Worksheet (11/17 – 11/23) SI Leader: Joy Chen Professors Lin & Song www.usc.edu/si Lin & Song Combined Worksheet Topics Stressed: Hypothesis Testing (Week 1 of 2) 1. Use the following data to determine whether or not to reject the null hypothesis: X-bar = 160; σ = 36; n = 36; H 0 : μ 140; H 1 : μ > 140; α = 0.05 2. We want to perform the hypothesis test: H 0 : μ = 30 H 1 : μ 30 Assume the population is normally distributed and σ = 4.5. Sample of size 25 is selected and X-bar is 32.5. a. At 2% significance level? b. At 0.5% significance level? 3. Mark is conducting a research on the height of the male population. From other studies, he knows that the height of the male population is normally distributed with standard deviation of 25cm. In order to test if the average height of the male population is greater than 175cm, he randomly picks 100 people, measures their heights and finds the average to be 180cm. Is the average height greater than 175cm? Use a significance level of α =0.03. a. Solve using the rejection region method. b. Solve using the p-value method. 4. In recent years, a number of companies have been formed that offer competition to AT&T in long-distance calls. All advertise that their rates are lower than AT&T’s, and as a result their bills will be lower. AT&T has responded by arguing that for the average consumer, there will be no difference in billing. Suppose a statistics practitioner working for AT&T determines that the mean and standard deviation of long-distance bills for all its residential customers are \$17.09 and \$3.87, respectively. He then takes a random sample of 100 customers and recalculates their last month’s bill using the rates quoted by a leading competitor and finds it to be \$17.55. Assuming that the standard deviation of the population is the same as for AT&T, can we

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Si - week 13 worksheet - MATH 218 SI Session(Fall 2008 Week...

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