User talk:Steven A Brown

The z-score measures how many standard deviations a data value is ABOVE the mean. Saying "above or below the mean", or "differs from the mean" is incorrect.

Example: z = -5

<=> -5 standard deviations ABOVE the mean

<=> 5 standard deviations BELOW the mean

It is incorrect to say z=-5 means that a data point "differs from the mean by -5 standard deviations", or "is above or below the mean by -5 standard deviations".