A random sample of 40 students has a mean annual earnings of

A random sample of 40 students has a mean annual earnings of $3120. Assume the population standard deviation is $677. Construct the confidence interval for the population mean, mu if c = 0.95. Determine the sampling error if the grade point averages for 10 randomly selected students from a class of 125 students has a mean of x = 2.8. Assume the grade point average of the 125 students has a mean of The mean score for all NBA games during a particular season was less than 104 points per game. If a hypothesis test is performed, how should you interpret a decision that rejects the null hypothesis? A local politician, running for reeled ion. claims that the mean prison time for car 20)_ thieves is less than the required 4 years. A sample of 80 convicted car thieves was randomly selected, and the mean length of prison time was found to be 3 years and 6 months, with a population standard deviation of 1 year and 3 months. At a = 0.05, test the politician\'s claim. In order to set rates, an insurance company is trying to estimate the number of sick days that full time workers at an auto repair shop take per year. A previous study indicated that the standard deviation was 2.8 days, How large a sample must be selected if the company wants to be 95% confident that the true mean differs from the sample mean by no more than 1 day? Repeat part (a) using a 98% confidence interval. Which level of confidence requires a larger sample size? Explain. In order to set rates, an insurance company is trying to estimate the number of sick days that 7 full time workers at an auto repair shop take per year. A previous study indicated that live standard deviation was 2.8 days. How large a sample must be selected if the company wants to be 95% confident that the true mean differs from the sample mean by no more than 1 day? A trucking firm suspects that the mean life of a certain tire it uses is less than 35,000 miles. To check the claim, the firm randomly selects and tests 18 of these tires and gets a mean lifetime of 34,350 miles with a standard deviation of 1200 miles. At a = 0.05, test the trucking firm\'s claim.

Solution