One number for the class
The teacher wants one number to sum up test scores: the mean averages them, the median finds the middle student, the mode is the most common score. One very high score drags the mean up but leaves the median calm — which is why we have all three.
Three ways to find the 'middle'
- Mean — add all values and divide by how many (the average)
- Median — the middle value when sorted
- Mode — the value that appears most often
Data: 3, 5, 5, 8, 9 mean = 30/5 = 6 · median = 5 · mode = 5
Lab · Find all three
- Take the data 2, 4, 4, 6, 9.
- Add them and divide by 5 for the mean.
- Sort them and pick the middle for the median; the most common is the mode.
What you should see: mean = 25/5 = 5, median = 4, mode = 4.