After selecting Histogram, a similar dialog box is displayed as for Summary statistics.
Enter the name of a variable and optionally a selection criterion. If you have previously entered this variable and selection criterion in the box for summary statistics, then this new variable will be selectable in the Variable list (click the button).
After you click OK the program collects the data, performs some initial calculations, and displays the following dialog box:
In this dialog box, the program gives the mean, standard deviation, minimum and maximum value for the selected variable. Next, the default lower and upper limits, and the default number of classes in the histogram are displayed. If you prefer other values than these default values, you can make the necessary changes. For Lower and Upper limit, the program will not accept values greater or less than the minimum and maximum of the variable. When you click OK, the program will continue with the new settings, but when you click Cancel, the program will display the histogram with the initial default settings.
This is the histogram for the variable Weight:
The first bar in this histogram represents the number of cases (frequency) with weight 55 and < 60. The second bar represents the number of cases with weight 60 and < 65, etc.
When the Show Normal distribution option is selected, a Normal distribution plot (with Mean and Standard Deviation of the data represented in the histogram) is superimposed over the histogram.
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 can not 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, see Format graph.
By selecting the Export command in the File menu you can export the displayed graph as a picture file (see Export graphs). When you want to print the graph, press Ctrl+P.