Ohio Assessments for Educators (OAE) Mathematics Practice Exam

Which measure of central tendency would be least affected by outliers?

1. Mean

2. Mode

3. Median

4. Range

The correct answer is: Median

The measure of central tendency that is least affected by outliers is the median. The median represents the middle value in a data set when the values are arranged in ascending or descending order. Because the median is solely dependent on the position of the data points rather than their actual values, extreme values (or outliers) do not influence it significantly. For instance, in a data set of 1, 2, and 1000, the median is 2, which remains unaffected by the outlier 1000. In contrast, the mean, which is the average of all values, can be heavily skewed by outliers; for example, adding a very large number to a small set of values can raise the mean considerably. The mode, which is the most frequently occurring value, can also be influenced by outliers if they become the most common value. The range, while not a measure of central tendency, is the difference between the maximum and minimum values in the set, making it extremely sensitive to outliers as well. Thus, the median maintains its integrity and represents a more accurate measure of central tendency in the presence of extreme values.