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:
- An Independent Samples t-test compares the means for two groups.
- A Paired sample t-test compares means from the same group at different times (say, one year apart).
- A One sample t-test tests the mean of a single group against a known mean.
- Choose confidence level
- Obtain sample mean of control group
- Obtain sample mean for experiment group
- Obtain sample deviation experiment group