T-Test Explained

T-test or also known as Student T-Test tells us whether a sample of numeric data strays or differs significantly from the population. It also talks about two samples- whether they’re different. In other words, it gives us the probability of difference between populations. The test involves a t-statistic. For small samples, we can use a T-test with two samples. It is generally used when the sample size is less than 30 and the SD of the population is unknown.

Independent two-sample t-test

An Independent (or unpaired two-sample) t-test is used to compare the means of two unrelated groups of samples. As an example, we have a cohort of 100 individuals (50 women and 50 men). The question is to test whether the average Salary of women is significantly different from that of men? In this case, we have two independents groups of samples and an unpaired t-test can be used to test whether the means are different.

where N1 and N2 represent the sizes of the group and X1 andX2 the mean of the groups

Paired t-test

Paired Student’s t-test is used to compare the means of two related samples. That is when you have two values (pair of values) for the same samples. For eg You started a training program in your firm and you want to check if there was any difference in the performance due to the training provided to the employees. So in that case Paired t-test can be used to check the before and after performance of the employees.