Confident Interval Essay

664 WordsNov 27, 20123 Pages
STA3003 Fall 2012 Assignment 5 (Total Points Possible: 15) Name: Banner ID: Instructions: Use this page as your cover page, and attach your groupwork behind your work. Your assignment answers should be in complete and grammatically correct sentences. 1. According to the National Center for Health Statistics (2004), 22.4% of adults are smokers. A random sample of 300 adults is obtained. (a) Describe the sampling distribution of phat, the sample proportion of adults who smoke. (b) In a random sample of 300 adults, what is the probability that at least 50 are smokers? (c) Would it…show more content…
Interpret the confidence interval. You wish to conduct your own study to determine the proportion of adult males 20 to 34 years old who have hypertension. (c) What sample size would be needed for the estimate to be within 3 percentage points (interval length is 0.06) with 95% confidence if you use the point estimate obtained in part (a)? (d) What sample size would be needed for the estimate to be within 3 percentage points with 95% confidence if you don’t have a prior estimate (use phat=.5)? 4. A random sample of 60 married couples who have been married 7 years was asked the number of children they have. The results of the survey are as follows: 0 0 0 3 3 3 1 3 2 2 3 1 3 2 4 0 3 3 3 1 0 2 3 3 1 4 2 3 1 3 3 5 0 2 3 0 4 4 2 2 3 2 2 2 2 3 4 3 2 2 1 4 3 2 4 2 1 2 3 2 The data is also in Excel format on Blackboard: FamilySizeData.xls. (a) Obtain a point estimate for the mean and standard deviation number of children of all couples who have been married 7 years. (b) What is the shape of the distribution of the sample mean? Why? (c) Compute a 95% confidence interval for the mean number of children of all couples who have been married 7 years. Interpret this interval. (d) Compute a 99% confidence interval for the mean number of children of all couples who have been married 7

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