NormalProbPlot.XLS Simulated Sampling for Practice in using Normal Probability Plots
by John O. McClain Links: [ Downloading
| Errors | Free Software | John McClain's Page ]
This workbook allows you to simulate the residuals from a
regression analysis, and displays them as a Histogram and as a Normal Probability
Plot. Samples are drawn from four different populations:
Clear differences are obvious when the sample size is several hundred, but when the sample size is small it is very difficult to determine whether the Histogram and Normal Probability Plot indicate a significant departure from normality. Contrasting the results for the different distributions shows you how much departure from the “ideal shapes” of these graphs should be expected.
This is a very simple simulator, intended for teaching purposes. You are welcome to use it in any manner, and change it as you see fit. This model comes without any guarantee whatsoever, and is distributed free of charge.
Warning: This workbook contains macros, so Excel may give you a warning when you open it. If you disable the macros, the simulation will not run.
Downloading
The file is about 0.2 megabytes in size. To download, click here and follow the prompts.
If the file
Doesn't Work:
Some users find that the buttons that I have imbedded in this Excel Spreadsheet
do not work. If this happens, Microsoft Excel has disabled the macros that the
buttons are supposed to run. To fix this (or to make sure it does not happen)
follow these steps:
1. Start Microsoft Excel.
2. On the Tools menu, point to Macro, and then click Security.
3. Click the Security Level tab.
4. Click Medium. Then click OK.
5. Exit from Excel.
6. Restart Excel and open the file. This time the computer should warn you that
there are macros.
Click Enable so the macros
can run.
"Medium Security" will cause your computer to warn you when an Excel File contains macros, giving you the chance to disable them if you do not trust the person who supplied the file.
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