Using the histogram it can be evaluated visually whether the data are distributed symmetrically, Normally 

or Gaussian or whether the distribution is asymmetrical or skewed. 

When the distribution is not Normal, it cannot accurately be described by mean and standard deviation, but 

instead the median, mode, quartiles and percentiles should be used.  The latter statistics are reported in 

the Summary statistics window. 

To change the titles, colors or axis scaling used in the graph, refer to page 11. 

By selecting the Export command in the File menu you can export the displayed graph as a picture file 

(see p. 21).  When you want to print the graph, press Ctrl+P. 

Cumulative frequency distribution 

To obtain a cumulative frequency distribution, select Cumulative frequency distribution in the menu and 

proceed as for Histogram. 

In the dialog box for Cumulative frequency distribution, you can either select a Cumulative frequency 

polygon or Cumulative dot plot, or both.   

Finally you have the option to superimpose a Normal distribution curve on the diagram.  The mean and 

standard deviation of this Normal distribution curve are those of the variable represented in the graph. 

When this option is selected the cumulative frequency distribution is plotted using a different algorithm, 

allowing comparison of the observed frequency distribution with the theoretical Normal distribution. 

When you have completed the dialog box, select the 

OK

 button, or press the Enter key to obtain the 

graph. 

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