A sporting equipment company manufactures 15 pond dumbbells .To ensure that the production line is functioning properly , 50 dumbbells were selected at random , and their weight were recorded .The observed sample mean weight of the 50 dumbbells was 16.87 lb and the observed sample standard deviation was 1.44 lb.       A Construct a 90% confidence interval for the mean of the distribution of the weight of the manufactured dumbbells

The International Air Transport Association surveys business travelers to develop quality ratings for transatlantic gateway airports. The maximum possible rating is 10. Suppose a simple random sample of 50 business travelers is selected and each traveler is asked to provide a rating for the Miami International Airport. The ratings obtained from the sample of 50 business travelers provides a mean of 6.34 and a standard deviation of 2.163. Develop a 95% confidence interval estimate of the population mean rating for Miami.

In a random sample of 17 people, the mean commute time to work was 30.2 minutes and the standard deviation was 7.1 minutes. Assume the population is normally distributed and use a t- distribution to construct a 95% confidence interval for the population mean y. What is the margin of error of y? Interpret the results.

A study of a local high school tried to determine the mean number of text messages that each student sent per day. The study surveyed a random sample of 114 students in the high school and found a mean of 195 messages sent per day with a standard deviation of 73 messages. Determine a 95% confidence interval for the mean, rounding all values to the nearest whole number.

In September a biological research team caught, weighed, and released a random sample of 24 chipmunks in Rocky Mountain National Park. The mean of the sample weights was x-bar = 8.7 oz. with sample standard deviation s = 1.4 oz. Find a 90% confidence interval for the mean September weight of all chipmunks in Rocky Mountain National Park.

A technician compares repair costs for two types of microwave ovens (type I and type II). He believes that the repair cost for type I ovens is greater than the repair cost for type II ovens. A sample of 35 type I ovens has a mean repair cost of $80.39. The population standard deviation for the repair of type I ovens is known to be $24.63. A sample of 31 type II ovens has a mean repair cost of $73.47. The population standard deviation for the repair of type II ovens is known to be $10.42. Conduct a hypothesis test of the technician's claim at the 0.05 level of significance. Let i be the true mean repair cost for type I ovens and µz be the true mean repair cost for type II ovens. Step 1 of 5: State the null and alternative hypotheses for the test.