Often called Student’s t-test. A statistical test of significance in which the difference between two mean values is tested. The null hypothesis is that there is no difference between the two means. The test is carried out by calculating a t-value, then comparing the calculated t-value with a critical t-value which is obtained from a statistics table. If the calculated t-value is greater than the critical t-value, the null hypothesis is rejected; this means that a statistically significant or real difference exists between the mean values being compared. If the calculated t-value is less than the critical t-value, the null hypothesis stands, therefore no difference has been observed between the two mean values.