Why use Normal Distributions?
What is important is to understand that the normal distribution is used very frequently because: • It can be shown that many characteristics of interest, such as IQ, height and weight of people, etc., have a normal population distribution. • It can be shown mathematically that this shape is guaranteed in certain situations that will be important to us in inferential statistics. Characteristics: The normal distribution: • is symmetrical (the left side is a mirror image of the right side). • has 50% of the scores below the mean and 50% above. (Mean = Median) • has most scores are in the middle. Few scores are at the edges. The Standard Normal Distribution A normal distribution is a Standard(ized) normal distribution when its scores are expressed in standardized z-scores. The standard normal distribution • has a mean of 0 and a standard deviation of 1, just like any other standardized distribution. • has a normal shape, just like any other normal distribution. For a standard normal distri
