Comparing measurements
Describe, interpret, and compare distributions of a single variable using appropriate measures of central tendency (mean, median, mode) and spread (range), including the effect of outliers
What a learner can do afterwards
- Calculate mean, median, and mode for a data set and explain when each is most appropriate
- Find the range of a data set and explain how an outlier affects the mean versus the median
- Compare two data sets using their averages and ranges to draw conclusions
The lesson
You already know how to find the mean: add up the numbers and divide by how many there are. Two more ways to find a typical value are the median and the mode. The median is the middle number when the data is lined up in order. The mode is the number that shows up most often. The range tells you how spread out the numbers are: the biggest number minus the smallest.
A team's ages are 12, 14, 12, 15, 12. Line them up in order: 12, 12, 12, 14, 15. The middle number is 12, so the median is 12. Since 12 shows up three times, more than any other age, the mode is also 12.
Watch out for outliers, numbers far away from the rest. An outlier can pull the mean up or down by a lot, but it barely changes the median, since the median only cares about the middle position. When a data set has an outlier, the median usually gives a fairer picture of what's typical.
Median is the middle value, mode is the most common value, and range shows the spread, but an outlier throws off the mean far more than the median.
Watch it
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.