What is mean, median, and mode?

Why it matters

These three "measures of center" are how kids start summarizing data — what a class typically scored on a test, what a player typically scores in a game. They also show up on every state test from Grade 6 on, and they’re the gateway to all of statistics.

Worked example

Find the mean, median, and mode of: 4, 8, 6, 8, 9.

1. 1

   Mean: add all the numbers, then divide by how many there are. Sum: 4 + 8 + 6 + 8 + 9 = 35. Count: 5 numbers.

   The mean spreads the total equally across all the data points.

2. 2

   Divide: 35 / 5 = 7. The mean is 7.

3. 3

   Median: line the numbers up in order from smallest to largest: 4, 6, 8, 8, 9. The middle number is the third one (since there are 5).

   When there’s an ODD count, the median is the single middle number. With an even count, you’d take the mean of the two middle numbers.

4. 4

   The third number is 8. The median is 8.

5. 5

   Mode: which value shows up most often? 8 appears twice; every other number appears once. The mode is 8.

   A data set can have one mode, more than one mode, or no mode at all if every value is unique.

Common mistakes

• •Forgetting to put the numbers in order before picking the median — grabbing the middle number from the list as given.
• •For an even count: picking just one of the two middle numbers instead of averaging them. The median of {2, 4, 6, 8} is 5, not 4 or 6.
• •Calling the most common LABEL the mode in a category — getting confused on categorical data ("which color is the mode?"), where mode is the correct measure but mean and median don’t apply.
• •Dividing the sum by the wrong count — including or skipping a value accidentally, especially when zeros are in the data set (zeros count as data points).

How Briveli teaches mean, median, and mode

Briveli covers mean, median, mode, and range in Grade 6 as a single unit on "measures of center" — and links them to data displays (dot plots, histograms, box plots) so kids see how each measure summarizes a graph differently.