Using the simple random sample of weights of women from a da

Using the simple random sample of weights of women from a data set, we obtain these sample statistics: n =40 and x = 147.95 lb. Research from other sources suggests that the population of weights of women has a standard deviation given by sigma = 31.4S lb. a. Find the best point estimate of the mean weight of ail women. b. Find a 90% confidence interval estimate of the mean weight of ail women. a. The best point estimate is [ ] lb. (Type an integer or a decimal.) b. The 90% confidence interval estimate is [ ] lb

Solution

(a) The best point estimate is 147.95 lb

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(b) Given a=1-0.9=0.1, Z(0.05) = 1.645 (from standard normal table)

So the lower bound is

xbar - Z*s/vn =147.95 -1.645*31.48/sqrt(40) =139.76

So the upper bound is

xbar + Z*s/vn =147.95 +1.645*31.48/sqrt(40) =156.14