Two Sample t-Test
To compare responses from two groups. These two groups can come from different experimental
treatments, or different natural "populations".
- each group is considered to be a sample from a distinct population
- the responses in each group are independent of those in the other group
- the distributions of the variable of interest are normal
How It Works
- The null hypothesis is that the two population means are equal to each other.
To test the null hypothesis, you need to calculate the following values:
means of the two samples), s12, s22
(the variances of the two samples), n1, n2 (the
sample sizes of the two samples), and k (the degrees of freedom).
- Compute the t-statistic.
- Compare the calculated t-value, with k degrees of freedom, to the
critical t value from the t distribution table at the chosen confidence
level and decide whether to accept or reject the null hypothesis.
*Reject the null hypothesis when: calculated t-value > critical t-value
- Note: This procedure can be used when the distribution variances from the two
populations are not equal, and the sample sizes are not equal.