Factors that influence a hypothesis test with the t statistic Suppose you conduct a hypothesis test about a population mean when the standard deviation is unknown calculating a t statistic and determining whether to reject the null hypothesis. Assume that your t statistic positive value and that you will reject the null hypothesis when t is very large. For each of the potential the components of your study design or the results listed below, determine the change to the t statistic, select "Increases, " "Decreases, " or "Stays the same" from the dropdown menu in the right-hand column.