F-distribution Probability
  This is a continuous distribution with positive values only. The operation is similar to the Chi-square distribution active table. The Tab key is used to move to the next editable field, and the Enter or Return keys will register a newly typed value. The graph is slightly harder to calculate and may take longer to plot. The maximum value is for the display purposes only, and can be set to high values especially when the degrees of freedom are very small. Study the F-distribution static tables for some idea of the values possible.
  The sliding control is used to dynamically alter the f value, and the other parameters affected by this change will update as well. The probabilities you can calculate are: F < f, and F > f.
  Be aware that the F-distribution plot requires intensive computations to make it reasonably smooth, and hence may take longer to replot than other distributions.