To determine whether to reject the null hypothesis using the t-value, compare the t-value to the critical value. If the absolute value of the t-value is greater than the critical value, you reject the null hypothesis. If the absolute value of the t-value is less than the critical value, you fail to reject the null hypothesis. You can calculate the critical value in Minitab or find the critical value from a t-distribution table in most statistics books. For more information on calculating the critical value in Minitab, go to Using the inverse cumulative distribution function (ICDF) and click Use the ICDF to calculate critical values.