A measure of center is a single, central value that summarizes a set of data.
The mean of a set of data values is the sum of the data divided by the number of data values.
data set: −5, −1, 3, 6, 8, 8, 9
For an odd number of data values, the median is the middle value when the data values are arranged in numerical order.
For an even number of data values, the median is the average of the two middle items when the data values are arranged in numerical order.
Example Finding Mean and Median Intervals
At Yellowstone National Park, Data Girl and Ms. Adventure watch Jewel Geyser erupt. Data Girl records the time intervals between eruptions.
a. Find the mean and median intervals between eruptions.
b. Using the measure of center, what inference can you make about how often Jewel Geyser erupts?