What is the difference between mean and median?

Document created by Community User on Oct 18, 2016Last modified by Community User on Jun 6, 2017
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Question
What is the difference between mean and median?

Answer
The mean is the arithmetic average of a group of scores. The median is the middle score in a list of scores; it is the point at which half the scores are above, and half the scores are below.

 
Why do we use the median in addition to the mean?

Medians are less likely to be skewed by an unusually high or unusually low score. Therefore, they are usually a better indicator of where the middle of the class is achieving, especially for smaller sample sizes (such as the size of a typical classroom). Means are most often used with larger sample sizes. Most MAP Growth reports provide both the mean and the median.

 
Do we use both mean and median in the norms study?

In the NWEA norms study, we only refer to the mean. This is because in a large, normally distributed sample (a "normal distribution"), the mean and the median are actually the same. This is why your reports will show the grade level mean RIT but not the median, since they are the same number.

 
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