Cumulative Plot

To generate a Cumulative Plot of any quantitative data column in Grid Data:

1. Select Statistics > Plot Cumulative.
2. In the Cumulative Plot Parameters dialog:
   1. Select a Data Type from the drop-down list. Any quantitative Grid Data column can be plotted.
      NOTE: Qualitative data will not be interpreted correctly as numeric data.
   2. Enter a Number of Intervals. The default is 30, but any value between 1 and 500 can be entered.
   3. Select the Attach Markers to Distribution check box to display interval Markers on the plot.
   4. Select OK to plot the cumulative plot.

The Cumulative Distribution will be generated, and the mean, standard deviation, minimum and maximum values for the data plotted, will be listed at the bottom of the plot.

A Cumulative Distribution is, mathematically speaking, the integral of the normalized probability density function. Practically speaking, a point on the cumulative distribution gives us the probability that a random variable will be LESS THAN OR EQUAL TO a specified value.

That is, if (X, Y) is a point on the cumulative distribution S-curve, then Y = the probability that the random variable will be <= X.

Right-click Options

Several viewing options are available when generating a Cumulative plot. These options are available on the Chart menu and/or the right-click menu.

• Sampler
• Chart Properties
• Copy Chart/Data to Clipboard
• Copy Picture to Clipboard
• Plot in Excel

Sampler

The Sampler option on a Cumulative Plot allows you to easily determine the coordinates at any point along the S-curve.

1. Right-click on the Cumulative Plot, and select the Sampler > Show Sampler option.
2. You will see a dotted cross-hair line on the plot. This is the “Sampler”, and allows you to graphically obtain the coordinates of any point on the curve.
3. As you move the mouse over the cumulative plot data, you will see that the Sampler follows the mouse, and continuously displays the coordinates of points on the cumulative plot.