Chi square Probability
  Enter the required values in the editable fields of the dialog box and the probability will be calculated when you press the Tab, Enter or Return keys. The Tab key will shift the insertion point to the next editable field. The graph of the chi-square distribution is always positive with a positive tail tapering to infinity. This can only be approximated when plotted (by checking the Show Graph check box (shortcut Command-S)), so a maximum value is indicated. To reduce the scale of the graph, you can also increase the value of this maximum value. This does not affect the calculated probability, only the displayed graph and hence area under the curve. Note that the only displayed probability is the area between 0 and the x value.
  Drag the sliding control to alter the x value dynamically.
  NOTE: the graph for chi-square will look unusual with very small degrees of freedom (1 & 2) because it asymptotically approaches both axes! The area filled in is the area under the curve, but may look very small, especially for 1 df.