Question

What is the difference between mean and median?

Answer

The

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.

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. ##

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

** **

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

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See also:

Article Number

3250