Math 221 – Principles of Statistics

Creating Histograms-With-Normal-Curves in SPSS

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A histogram is a bar graph for binned quantitative data, in which the heights of the bars represent frequency or relative frequency, and there are no gaps between the bars. Adding the appropriate Normal curve to the histogram can help you assess Normality.

 

To create a histogram-with-Normal-curve in SPSS:

 

1) Open a data file (in .sav or .por format) or type your data in.

 

2) In either the Data Editor window or the Output Viewer window, click on the “Graphs" menu and then on "Histogram..."

 

3) Select the variable of interest. Click on the little arrow next to "Variable." This will move the variable into the "Variable" box.

 

4) Click the check box next to "Display normal curve."

 

5) If you would like to add a title to your plot, click the "Titles..." button. A new dialog box appears. Enter any titles or subtitles you want to use, and click "Continue..."

 

6) Click "OK."  The graph appears in the Output Viewer. If you would like to change the label on the vertical axis, or change the bin width or the anchor of the first bin, use the Chart Editor.

 

NOTE: The Normal curve that SPSS puts on the histogram is the Normal curve with the same mean and standard deviation as the data have. It turns out that if the data are Normal, then the Normal curve on the screen represents the particular Normal distribution the data come from.

 

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David E. Brown

BYU-Idaho                                            mailto:brownd@byui.edu

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