Z-Scores
A z-score, sometimes called a standardized score, is
simply the number of standard deviations an observation is
from the mean. It is found by subtracting the mean and then
dividing by the standard deviation, or:
z=(x-µ)/σ
The equation has four variables. If you know any three,
you can solve for the fourth.
Finding z-scores is an essential step in using the Normal
probability distribution if people use tables rather than
having a computer do the computation. (If you have data that
is normally distributed (a topic of an upcoming section),
converting to z-scores gives transformed numbers with a mean
of zero and a standard deviation of one.)
|