To test whether the regression coefficient
Since this is a two-tailed test at a significance level of
-
Determine the degrees of freedom (df). For simple linear regression with one predictor, the degrees of freedom can be calculated as:
where
is the number of observations. In your case, , so: -
Find the critical t-values for a two-tailed test at
with 4 degrees of freedom. You can look these values up in a t-distribution table or use statistical software.
For a two-tailed test with
- The critical t-values can be found by looking up
in a t-table.
Using a t-table or calculator:
- The critical t-value for
and (each tail) is approximately .
Thus, the critical values to test the regression coefficient
Critical values: