The mean is the sum of all the scores divided by the number of scores.
N refers to the sample size.
The formula for M is the same as the formula for m . The mean is a good measure of central tendency for roughly symmetric distributions but can be misleading in skewed distributions since it can be greatly influenced by extreme scores. Therefore, other statistics such as the median may be more informative for distributions such as reaction time or family income that are frequently very skewed. Click here for an interactive demonstration of properties of the mean and median. The sum of squared deviations of scores from their mean is lower than their squared deviations from any other number.