**Definitions:
Means, Medians and Standard Deviations**

** Mean:** The average of all the values
of a variable such as age, weight-for-age z-score, income, or hemoglobin level.

** Median:** The middle value in a
distribution of values in a variable-- the value at which 50% of cases are above and 50%
are below.

If the median differs much from the mean value, then investigate the overall distribution of values.

** Standard Deviations:** The standard
deviation indicates the variation in the group of measurements. When the values of a set
of observation lie close to the mean, the dispersion is less than when they are scattered
over a wide range. A difference in the standard

deviation of a variable when comparing different groups will indicate possible data errors.