7. For each of the following, calculate the degrees of freedom, identify the critical values, calculate the t-statistic, and make a decision about the null hypothesis. a. Sample mean= 2.50, population mean= 3.50, standard error of the mean= .67, N=9 b. Sample mean= 2.50, population mean= 20, standard error of the mean= 2.00, N=16 c. Sample mean= .78, population mean= .59, standard error of the mean= .09, N=14