Extreme scores and the Mean

Question

How do extreme scores affect the mean?

Answer 1

Extreme scores will change the mean, but they typically do not affect the median, although it may change slightly. Think of a set of numbers such as 8, 9, 9, 10, 8, 10. The mean of this set of data is 9. Now add the number 20 to this list and calculate the mean. The mean will be higher. If you add the number 1 to the original set of numbers, you will get a mean that is lower. So an extreme value will increase the mean if it is higher than the rest of the values, but it will decrease the mean if it is lower than the rest of the numbers.