We would like to estimate the true mean number of hours that adults sleep at night. Suppose that sleep time is known to follow a Normal distribution with standard deviation 1.3 hours. For a sample of 18, what is the margin of error for a 95% confidence interval? Round to two decimal places.
We would like to estimate the true mean number of hours that adults sleep at night. Suppose that sleep time is known to follow a Normal distribution with standard deviation 2.6 hours. What sample size is required in order to estimate the true mean to within 0.4 hour with 96% confidence? Round up to the next whole number (ceiling).
The response times of technicians of a large heating company follow a Normal distribution with a standard deviation of 7 minutes. A supervisor suspects that the mean response time has increased from the target of 27 minutes. He takes a random sample of 29 response times and calculates the sample mean response time to be 32.3 minutes. What is the value of the test statistic for the appropriate hypothesis test? Round to two decimal places.
A researcher wants to know whether the average time in jail for robbery has increased from what it was several years ago when the average sentence was 7 years. The researcher obtains data on 400 more-recent robberies and finds an average time served of 7.5 years. If we assume the standard deviation is 3 years, what is the P-value of the test? Round to four decimal places.
What is the P-value for a test of the hypotheses H0: μ = 10 against Ha: μ ≠10 if the calculated statistic is z = 2.56? Round to four decimal places.