As with all of the hypothesis tests we have looked at in this chapter, once we have a statistic and a distribution, we simply need to pick a value of α and see if our data has exceeded the critical value for the test.
Incanter provides an
s/f-test function, but this only measures the variance between and within the two groups. To run an F-test on our 20 different groups, we will need to implement our own F-test function. Fortunately, we've already done the hard work in the previous sections by calculating an appropriate F-statistic. We can perform the F-test by looking up the F-statistic in an F-distribution parameterized with the correct degrees of freedom. In the following code, we will write an
f-test function, which uses this to ...