Which average is affected most by outliers?

Which average is affected most by outliers?

• A. Mean
• B. Median
• C. Mode
• D. Range

Answer: (A)

When considering averages, the mean uses every data point, so an extreme value pulls it toward itself. An outlier—like a very large or very small number—shifts the total sum and, because you divide by the count, the mean moves noticeably. The median, by contrast, is the middle value when the data are ordered, so a single outlier doesn’t change it much unless the sample is very small or the outlier changes which value sits in the middle. The mode is the most frequent value, so a lone outlier doesn’t typically alter it. The range, while affected by outliers, is a spread measure rather than an average, so it doesn’t address the question of which average is influenced most. For illustration, take data like 2, 3, 3, 4, 100. The mean becomes 22.4, whereas the median is 3 and the mode is 3. The outlier 100 drags the mean far upward, showing why the mean is the most sensitive to outliers.

When considering averages, the mean uses every data point, so an extreme value pulls it toward itself. An outlier—like a very large or very small number—shifts the total sum and, because you divide by the count, the mean moves noticeably. The median, by contrast, is the middle value when the data are ordered, so a single outlier doesn’t change it much unless the sample is very small or the outlier changes which value sits in the middle. The mode is the most frequent value, so a lone outlier doesn’t typically alter it. The range, while affected by outliers, is a spread measure rather than an average, so it doesn’t address the question of which average is influenced most.

For illustration, take data like 2, 3, 3, 4, 100. The mean becomes 22.4, whereas the median is 3 and the mode is 3. The outlier 100 drags the mean far upward, showing why the mean is the most sensitive to outliers.