Graph Software for Scientists and Engineers

Probability Scale

A probability scale is primarily useful in statistical studies. It will show the cumulative distribution function of a normally distributed variable as a straight line.

Normal distributions

The cumulative distribution function of a standard normal distribution (mean=0, standard deviation=1) is simply the integral of the normal distribution curve. Cumulative distributions for the data graphed above are shown on a linear scale here:

Cumulative distribution function, linear scale

The amplitudes of these curves have been multiplied by 100. By default DPlot works with probabilities within the range 0-100, exclusive, while other applications may express probabilities in the range 0-1. If you are working with probabilities ranging from 0 (no chance) to 1 (certainty), you can multiply those amplitudes by 100 so that they may be plotted on a probability scale in DPlot. Select Edit>Operate on Y and type "Y*100" for f(Y).

Right-click on the graph and select Linear X - Probability Y to get:

Cumulative distribution function, linear scale

Alternative to multiplying your probability values by 100 (in the case of a 0-1 range), after setting the scaling you can right-click on the graph, select Probability Scale Options, then select 0 < p < 1 under Input Range.


Windows 10,
Windows 8,
Windows 7, 2008,
Vista, XP, NT,
ME, 2003, 2000,
Windows 98, 95
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