How it works: The calculator above takes the place of the traditional textbook table. First, enter the appropriate number of degrees of freedom in the top two boxes. Then, the calculator can be used in two ways. To find F critical values, enter a probabilitiy in the "=" box and hit "Compute!". The answer is displayed in the "Area right of" box. To find tail probabilities (or p-values), enter the F value in the "Area right of" box and hit "Compute!". The probability will be displayed in the "=" box. In either case, the probability is represented graphically.