Exam 9: Statistical Inference: Hypothesis Testing for Single Populations

The local oil changing business is very busy on Saturday mornings and is considering expanding.A national study of similar businesses reported the mean number of customers waiting to have their oil changed on Saturday morning is 3.6.Suppose the local oil changing business owner, wants to perform a hypothesis test.The null hypothesis is the population mean is 3.6 and the alternative hypothesis is the population mean is not equal to 3.6.The owner takes a random sample of 16 Saturday mornings during the past year and determines the sample mean is 4.2 and the sample standard deviation is 1.4.It can be assumed that the population is normally distributed.The level of significance is 0.05.The decision rule for this problem is to reject the null hypothesis if the observed "t" value is _______.

In performing a hypothesis test where the null hypothesis is that the population mean is 4.8 against the alternative hypothesis that the population mean is not equal to 4.8, a random sample of 25 items is selected.The sample mean is 4.1 and the sample standard deviation is 1.4.It can be assumed that the population is normally distributed.The degrees of freedom associated with this are _______.

In testing a hypothesis about a population mean with an unknown population standard deviation ( $\sigma$ )the degrees of freedom is used in the denominator of the test statistic.