Take the following steps to answer probability questions using this table: With the Unit Normal Table: The unit normal table provides a listing of proportions (probabilities) corresponding to many z-scores in the standard normal distribution. 34.13% of the scores are between the mean and -1.00.34.13% of the scores are between the mean and +1.00.has a normal shape, just like any other normal distribution.įor a standard normal distribution it can be shown that.has a mean of 0 and a standard deviation of 1, just like any other standardized distribution.
Few scores are at the edges.Ī normal distribution is a Standard(ized) normal distribution when its scores are expressed in standardized z-scores. has 50% of the scores below the mean and 50% above.is symmetrical (the left side is a mirror image of the right side).It can be shown mathematically that this shape is guaranteed in certain situations that will be important to us in inferential statistics.Ĭharacteristics: The normal distribution:.It can be shown that many characteristics of interest, such as IQ, height and weight of people, etc., have a normal population distribution.Why use Normal Distributions? What is important is to understand that the normal distribution is used very frequently because: Normal Distribution Definition The normal distribution is defined by a complicated equation that we don't need to know or understand. Probability and Distributions: Gravetter & Wallnau, Chapter 6 Copyright © 1997-8 by Forrest W.
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