Example Ptoblems For problems 8 and 9, use the following problem description The

Question

Example Ptoblems For problems 8 and 9, use the following problem description The true average weight of a 20-yr-old MTSU female student is unknown but we will assume that the true standard deviation is 14 pounds. We assume that there are 3,000 20-yr-old MTSU female students. We wish to develop estimates of the true average weight. 8. A random sample of 36 (sampled without replacement) yielded a sample mean of 125 pounds with a sample standard deviation of 12.8 pounds. Find the 98% confidence interval estimate of the population mean. 4:33 witha sample standard deviation of 13.6 pounds. Find the 99% confidence interval estimate of the population mean. For problems 10 and 11, use the following problem description. The true average weight of a 20-yr-old female is unknown. The true standard deviation is also unknown. We are willing to assume that the weights of 20-yr-old females are normally distributed A random sample of 36 (sampled without replacement) yielded a sample mean of 125 pounds with a sample standard deviation of 2.8 pounds. Find the 98% confidence interval estimate of the population mean. 10. 11. A random sample of 61 (sampled without replacement) yielded a sample mean of 128 pounds with a sample standard deviation of 13.6 pounds. Find the 99% confidence interval estimate of the population mean For problems 12 and 13, use the following problem description. Suppose that we take a simple random sample of 64 20-yr-old females and find five that weigh ess than 100 pounds. 2. Find the 90% confidence interval estimate of the true population proportion of 20-yr-old females that weigh less than 100 pounds. ·Find the 99% confidence interval estimate of the true population proportion of 20-yr-old females who weigh less than 100 pounds. r problems 14 and 15, use the following problem description. e true proportion of 20-yr-old MTSU female students that weigh less than 100 pounds i known. We assume that there are 3,000 20-yr-old MTSU female students. We wish to elop estimates of the true population proportion that weigh less than 100 pounds. A random sample of 64 (sampled without replacement) contained seven who weigh than 100 pounds. Find the 98% confidence interval estimate of the population prop

Explanation / Answer

At 98% cinfidence interval the critical value is t0.99, 35 = 2.438

Confidence interval = mean +/- t0.99, 35 * sd/ sqrt (n)

= 125 +/- 2.438 * 12.8/sqrt(36)

= 125 +/- 5.2

= 119.8, 130.2

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