The standard deviation, like the mean, is used to analyze scaled, normally distributed data such as speed, weight, height, and temperature. It measures how spread out numbers are from the average (mean) value. The mean should only be used when the data follows a more or less normal distribution, as outliers in skewed distributions overly influence the mean.

1. Like the MEAN - the STANARD DEVIATION is used
when BOTH of the following conditions are met:
(1) data is SCALED
AND
(2) distribution is NORMAL
Data with equal intervals like speed, weight,
height, temperature, etc.
Because the mean is sensitive to outliers
that are found in SKEWED distributions, you
should only use the mean when the
distribution is more or less normal.