Definition
Median
The middle value after data are ordered, or the mean of the two middle values.
What it means
First line the values up from least to greatest. Cross off one value from each end until you reach the middle. If one value remains, it is the median. If two values remain, add those two and divide by 2.
Remember it
Order first, then meet in the middle.
Example
Order 9, 2, 7, and 4 as 2, 4, 7, 9. The two middle values are 4 and 7, so the median is (4 + 7) ÷ 2 = 5.5.
Watch for
The median is not simply the value written in the middle position before the data are ordered. With an even number of values, it may not be one of the original values.
Common mix-up
Median means the ordered middle; mean is found by adding all the values and dividing by how many there are.
Exact meaning
The median of an ordered numerical data set is its middle value when the number of values is odd. When the number is even, the median is the arithmetic mean of the two middle values.