A researcher is investigating the length of time that postal employees work for the U.S. postal service. Specifically, he is testing the hypothesesH0:= 7.6 andHa: 7.6 to determine if there is evidence that the meantime has changed from the 7.6 years known to be true 20 years ago. Using an SRS of 100 postal employees he found that the average time these employees had worked for the postal service was= 6.9 years, with standard deviations= 2.1 years. Assume the distribution of the time the population of employees has worked for the postal service is approximately Normal, with mean. Let= 0.05.

Reference: Ref 3

The appropriate degrees of freedom for thet-test are: