Question

15) Find the critical value that defines the rejection region for the following hypothesis test: Is the average life expectancy of Americans more than 78.8 years? To test this claim, a sample of 400 Americans are studied, with an average lifespan of 79.4 years and a standard deviation of 3.9 years. Use a significance level of 0.05. A) 1.649 B) 1.645 C) 3.08 D) -1.649 E) None of the Above 16) A large software company gives job applicants a test of programming ability. In the past the mean score for the test has been 160. Twenty-five applicants are randomly selected from one large university and they produce a mean score of 165, with a standard deviation of 13. At a significance level of 0.05, does this indicate that the sample comes from a population with mean score greater than 160? A) No. With a p-value of 0.0664, we fail to reject the null hypothesis. B) Yes. With a p-value of 0.0332, we reject the null hypothesis. C) No. With a p-value of 0.9336, we fail to reject the null hypothesis. D) Yes. With a p-value of 0.0024, we reject the null hypothesis. E) None of the Above 17) Is the mean lifetime of a particular type of car engine greater than 220,000 miles? To test this claim, a sample of 23 engines is measured, yielding an average of 226,450 miles and a standard deviation of 11,500 miles. Use a significance level of 0.01. A) FTR H, NEETS B) FTR H, NEETR C) Reject H, IEETR D) Reject H, IEETS E) None of the Above

Answer 1

sol (15) to distribution We we t critical value ta, nul - to.os, 400-1 toos, 399 1.649 " option (A) 16 Hoi U= 160 Ha : lu > 160 Test statistics 165-160 t = X-l sin 1.92 al 131 ves P-value : p(t, n-1) - P (1.92, 24) = 0.0332 option (B) yes, with P-value of 0.0332 the hull hull hypothesis. CS We reject Scanned with CamScanner