When a team is faced with a condition where they only have available to them small sample sizes (< n = 30) and they want to find the difference between two means, they would use a t-test based on the t distribution. (also known as student t distribution).
Use: To compare the difference between two means using a t-test is much like the method for using larger samples, however for small sample sizes; we need to use the t table for critical values instead of the Z table for the normal distribution. So, samples >30, use the Z table. For samples <30, use the t-table.
