Here is a full lecture on the F-test which I gave today

We multiply the statistic by (N-K)/(K-1) because it allows us to determine the distribution of the statistic for . any. linear model and . any. amount of data. If Ho is true then the statistic is distributed as an FK-1 ,N-K distribution. Textbooks on econometrics will have F distribution tables. You can also find such tables on the Internet. ................
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