1. A recent survey reported that small businesses spend 30 hours a week marketing their business. A local chamber of commerce claims that small businesses in their area are not growing because these businesses are spending less than 30 hours a week on marketing. The chamber conducts a survey of 94 small businesses within their state and finds that the average amount of time spent on marketing is 28.3 hours a week. Assuming that the population standard deviation is 8.8 hours, is there sufficient evidence to support the chamber of commerce's claim at the 0.01 level of significance?

Compute the value of the test statistic. Round your answer to two decimal places.

2. Thompson and Thompson is a steel bolts manufacturing company. Their current steel bolts have a mean diameter of 149 millimeters, and a standard deviation of 5 millimeters.

If a random sample of 49 steel bolts is selected, what is the probability that the sample mean would be less than 150.4 millimeters? Round your answer to four decimal places.

3. An independent group of food service personnel conducted a survey on tipping practices in a large metropolitan area. They collected information on the percentage of the bill left as a tip for35 randomly selected bills. The average tip was12.9% of the bill with a standard deviation of 2.2%. Assume that the tips are approximately normally distributed. Construct an interval to estimate the true average tip (as a percent of the bill) with90% confidence. Round the endpoints to two decimal places, if necessary.