Suppose average pizza delivery times are normally distributed with an unknown population mean and a population standard deviation of 6 minutes. A random sample of 28 pizza delivery restaurants is taken and has a sample mean delivery time of 36 minutes. What is the correct interpretation of the confidence interval?

Suppose average pizza delivery times are normally distributed with an unknown population mean and a population standard deviation of six minutes. A random sample of 28 pizza delivery restaurants is taken and has a sample mean delivery time of 36 minutes.  Find a 90% confidence interval estimate for the population mean delivery time.

On average, adults spend approximately 5 hours per night in NREM (non-rapid eye movement) sleep. A sleep study selects a random sample of adults and gives them each a weighted blanket. They would like to know if using the weighted blanket changes the mean number of hours per night of NREM sleep. We want to test  = 5 versus  ≠ 5 where  = the true mean hours of NREM sleep per night for adults who use a weighted blanket. A 99% confidence interval for the true mean hours of NREM sleep per night for adults who use a weighted blanket is (5.1, 5.8) hours. Based on the confidence interval, what conclusion would you make for a test of these hypotheses? The 99% confidence interval  include  as a plausible value, so we would  H0. We  convincing evidence that the true mean hours of NREM sleep per night for adults who use a weighted blanket  5 hours.

Calculate the 95% confidence interval and the 99% confidence interval for a sample of 81 where the population has a mean of 50 and a standard deviation of 6.

Sales personnel for City Distributors Inc. submit weekly reports listing the customer complaints made during the week. A simple random sample of 8 weekly reports showed a sample mean of 8 complaints per week with a sample standard deviation of 3.464. What is the 95% confidence interval for the population mean?

An agriculture researcher plants twenty five plots with a new variety of corn. The average yielded for these plots is x-bar = 150 bushels per acre. Assume that the yield per acre for the new variety of corn follows a normal distribution with unknown mean and standard deviation = 10 bushels per acre. A 90% Confidence interval for mean is?

According to a study of 90 truckers, a trucker drives, on average, 560 miles per day.  If the standard deviation of the miles driven per day for the population of truckers is 40, find the 95% confidence interval of the mean number of miles driven per day by all truckers.

A random sample of 49 Europeans was asked how many days of vacation they take each year.  The sample mean was 30 and the population standard deviation is known to be 4.  What is the 99% confidence interval of the true population parameter describing average vacation days?

Suppose that the population standard deviation of a student's score is 20. Choose a sample size so that the resulting 95% confidence interval for the population mean score has a margin of error no larger than 5.

An agricultural researcher plants 14 plots with a new variety of corn. The average yield for these plots is X = 155 bushels per acre. Assume that the yield per acre for new variety of corn follows a normal distribution with unknown mean and a calculated sample standard deviation s = 10 bushels. A 90% confidence interval for the unknown mean is