t-test is used when population true standard deviation is not known Instead sample deviation is used. But in this case test statistic distribution won’t be normal distrubution but t-distrubution wih n-1 degrees of freedom (where n is sample size). The more degrees of freedom t-distrubution has the more it closer to normal distrubution.

There are three main types of t-test:

  1. Choose confidence level
  2. Obtain sample mean of control group
  3. Obtain sample mean for experiment group
  4. Obtain sample deviation experiment group