# MandysNotes

Friday, 22 January 2010 23:54

## Mean vs. Median - Which is Better?

Rate this item
(1 Vote)

Both the mean and the median are measures of center.

If you have a symmetrical set of data -- IF THE NUMBERS IN THE SET ARE EVENLY SPACED -- the mean and the median will be EXACTLY THE SAME.

Here is WHY:

If you have a data set: 25, 50, 75

MEAN = (25 + 50 + 75) = 150 / 3 = 50

MEDIAN = 50 (the number bang in the center)

Both values are the same.

When dealing with skewed data sets (when the numbers are NOT evenly spaced), it is better to use the median to express the center.  It is RESISTANT to extreme values.

Here is WHY:

If you have a data set: 20, 50, 100

MEAN = (20 + 50 + 100) / 3 = 56.6666666

MEDIAN = 50

If we make this set even more extreme: 10, 50, 150

MEAN = (10 + 50 + 150) / 3 = 53.333333

MEDIAN = 50

No matter how we change the values in this set, if the middle number is 50, the MEDIAN will be 50.  ALWAYS.

The mean is SENSITIVE to change by every value, and therefore should only be used where the data is normally distributed.

I always remembered this by memorizing that we are all "sensitive to mean [people]" - but whatever works for you!