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by Gary H. McClelland

Probabilities for the Normal Distribution

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Enter beginning and ending z-scores in the Start and End boxes. The figure is redrawn and the new probability is calculated after hitting the return key while the cursor is in one of the boxes.

For open-ended ranges (i.e., finding the proportion of observations that will lie below a given value or above a given value), use a very large number for the other end (10 is large in this context).

Change the numbers in the Mean and StDev boxes as appropriate and then enter the appropriate Start and End values. Remember to hit the Return key in the last box you enter to start the calculations and redrawing.

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WARNING: The graph above gives accurate normal probabilities suitable for educational purposes such as homework problems. It is not intended for and should not be used for any calculations which have any major consquences for health, safety, financial matters, etc.

The above applet is from the section "Working with the Normal Distribution" in Seeing Statistics by Gary McClelland. For more information, visit Seeing Statistics

© 1999, Duxbury Press