The student t-test is used to compare the means of data values of two populations.The sample sizes may be different, but the data must be normally distributed and the sample size must be large enough to be reliable.A null hypothesis is stated predicting there is no significant difference between the means and that any observed difference is due to chance alone. The alternative hypothesis is that there is a significant difference between the means and the difference is not due to chance.The students t-test then determines if there is a statistical difference between the means.For the data to be considered significantly different from chance alone the probability of the value obtained are different must be 5% or less.This means that we have to be 95% confident that the difference is not due to chance.The formula for the students t-test is: