The response time of a server was measured 5 times, giving 20, 3, 5, 3 and 4 milliseconds in the order measured. Which of the following is the median of these data?

Answer: A. 4 milliseconds

The median is the middle value when the data are sorted by size. Sorted, the data are 3, 3, 4, 5, 20, so the median is the third value, 4 milliseconds. The mean is 35 ÷ 5 = 7 milliseconds, pulled up by the single large value of 20 milliseconds. The median is a measure of central tendency that is little affected by such outliers, and the mode, the most frequent value, is 3 milliseconds.

• A. Correct. It is the middle value of 3, 3, 4, 5, 20.
• B. This is the middle value in the order measured. The median is found after sorting the data by size.
• C. 7 milliseconds is the mean, which is strongly affected by the outlier of 20 milliseconds.