An introduction to averages: learn mean, median, and mode, see how outliers can change what “typical” looks like, and try quick activities that turn real data into a single useful number.
The Mystery of the Quiz Scores
Ms. Rivera’s class just finished a math quiz. Here are the results (out of 10):
| Student | Score |
|---|---|
| Alex | 9 |
| Ben | 7 |
| Cora | 8 |
| Dan | 10 |
| Ella | 6 |
Ms. Rivera asks,
“What’s the average score?”
The class quickly starts calculating.
Add them up → 9 + 7 + 8 + 10 + 6 = 40
Divide by 5 students → 8
“So,” says Ms. Rivera, “the typical score was about 8.”
Even though not everyone got an 8, that single number helps describe the whole group.
That’s the power of averages!
Averages, Medians, and Modes
There are three main ways to find what’s “typical” in a group of numbers:
| Type | How It Works | Example (6, 7, 8, 9, 10) |
|---|---|---|
| Mean (Average) | Add them up, divide by how many | (6+7+8+9+10)/5 = 8 |
| Median | The middle number when sorted | 8 |
| Mode | The most common number | (None in this case) |
Sometimes, these give similar answers — but not always!
The Outlier Problem
Now imagine Dan retakes the quiz and scores 0
The new scores are: 9, 7, 8, 0, 6.
- Mean = (9+7+8+0+6)/5 = 6
- Median = 7
See what happened?
One strange number pulled the mean down — that’s an outlier.
The median stayed closer to what’s typical.
So different averages tell different stories.
Activity 1 — Your Class in Numbers
- Pick a measurement for your class or friends (e.g. shoe sizes, heights, favorite game ratings).
- Write them down and find:
- The mean
- The median
- The mode
- Discuss: Which best describes your group?
- Add a wild number (like a super tall friend or a score of 0) and see what changes.
Challenge: Which average do you trust more when data has outliers?
Activity 2 — Guess the Average!
Write 5 mystery numbers on sticky notes.
Tell your friend only the average.
Can they guess your numbers?
Hint: Probably not — because averages summarize, but they don’t tell the whole story.
How This Connects to Machine Learning
When computers look at thousands (or millions!) of numbers, they can’t remember them all individually.
Instead, they summarize data — using averages or similar math — to understand what’s typical.
For example:
- A movie app averages your ratings to suggest new films
- A weather model uses average temperatures to predict next week
- A robot uses averages to understand what a “normal” movement looks like a robot
In machine learning, finding “average” patterns helps models simplify complex data.
Takeaway Message
Averages help us tell big stories with small numbers.
They’re the bridge between lots of messy data and clear insights — for humans and machines.
Optional Extensions
For Teachers / Parents / Older Students:
- Show how outliers affect averages using spreadsheet formulas.
- Plot scores on a bar graph — visually highlight the mean and median.
- Discuss weighted averages (like GPA or final grades).