Also, the intro of that page contains blatantly incorrect statements:

>"In the significance testing approach of Ronald Fisher, a null hypothesis is rejected if the observed data are significantly unlikely to have occurred if the null hypothesis were true. In this case the null hypothesis is rejected and an alternative hypothesis is accepted in its place."

There is no alternative hypothesis in Fisher's significance testing.

Here is a better wikipedia page:

"We may, however, choose any null hypothesis we please, provided it is exact."-Ronald Fisher https://en.wikipedia.org/wiki/The_Design_of_Experiments

I've heard that a lot of math fields really fail to teach history, perhaps that is what happened in your stats program.