Critical value = This is the value that the calculated t-value must exceed in order to reject the null hypothesis. It can be found in a t-distribution table based on the chosen alpha level (0.05) and the degrees of freedom. 95% confidence interval for the mean difference= This is a range of values that is likely to contain the true mean difference 95% of the time. It is calculated as: (M1 - M2) (t*SE), where t is the critical t-value