Median - The middle value, or the mean of the middle two values of a data set when the data is arranged in numerical order. Think of a "median" being in the middle of a highway.
Medians are less sensitive to extreme scores and are probably a better indicator generally of where the middle of the class is achieving, especially for smaller sample sizes. Means are the arithmetic average and are often used with larger sample sizes.
The mean and median each have advantages and disadvantages when used to describe data sets. The mean depends on the actual values in a data set, but the median is dependent only on the relative position of the values. Changing one data value does not affect the median, unless the data value is moved across the middle of the data set. But every change in a data value affects the mean. Thus, the mean is affected by a few extremely large or extremely small values outside the range of the rest of the data, but the median is not.
Use the median to describe the middle of a set of data that does have an Outlier. Advantages:
• Extreme values (outliers) do not affect the median as
strongly as they do the mean. • Useful when comparing sets of data. • It is unique - there is only one answer.
• Not as popular as mean.
Also see Mean.