A random sample (n = 25) of student GPA produces a mean of 3.2 and a standard deviation of 1.1. Find the test statistic for a claim that the mean GPA is less than 3.7.

The sample mean of depression scores of 16 fifth graders was 4.4 with standard deviation of 8. If the population mean of this depression score is 6, what is the calculated t score for this sample?

Many people believe that the average number of Facebook friends is 328. The population standard deviation is 32.2. A random sample of 60 high school students in a particular county revealed that the average number of Facebook friends was 340. At α = 0.05, is there sufficient evidence to conclude that the mean number of friends is greater than 328?

A telephone company claims that the mean duration of a long-distance phone calls made by its residential customers are 10 minutes. A random sample of 86 long-distance calls made by its residential customers taken from the records of this company showed that the mean duration of calls for this sample is 9.20 minutes. The population standard deviation is known to be 3.80 minutes. Test the claim that the mean duration of a long-distance phone calls is less than 10 minutes. Use a = 0.05. Answer the following questions. a. Identify the claim and state the Ho and H1. b. Find the critical value. c. Calculate the test statistic. d. Make a decision to reject or fail to reject the Ho. e. Interpret the decision.