Data & Probability · Measures of center · 1.1

Mean (average).

The mean — the everyday “average” — evens the data out: add up all the values and divide by how many there are. For 4, 8, 6, 2: (4+8+6+2) ÷ 4 = 5.

01 / THE IDEA

See it work.

The data

See the values.

41826324

Watch the method

Mean (average)

Mean = sum of values ÷ number of values.

1 / 2
Find the mean of: 4, 8, 6, 2.
1

Add the values

Find the total of every value in the set.

4+8+6+2=204 + 8 + 6 + 2 = 20
2

Divide by how many

The mean is the total divided by the number of values.

204=5\frac{20}{4} = 5
02 / YOUR TURN

Practice until it feels automatic.

Your turn

Work it out.

Type the answer — a fraction or decimal is fine.

streak 0
best 0

…

— / WHY IT WORKS

The idea underneath.

Share it equally

The mean is what each value would be if the total were shared evenly.

Why it works

Level the bars to the same height.

03 / WORKED EXAMPLES

From easy to tricky.

EX 1easy

Find the mean of: 8, 12, 5, 8, 11, 6.

1

Add the values

Find the total of every value in the set. 8 + 12 + 5 + 8 + 11 + 6 = 50

2

Divide by how many

The mean is the total divided by the number of values. 50/6 = 25/3

EX 2medium

Find the mean of: 5, 3, 10, 4.

1

Add the values

Find the total of every value in the set. 5 + 3 + 10 + 4 = 22

2

Divide by how many

The mean is the total divided by the number of values. 22/4 = 11/2

EX 3hard

Find the mean of: 5, 4, 5, 10.

1

Add the values

Find the total of every value in the set. 5 + 4 + 5 + 10 = 24

2

Divide by how many

The mean is the total divided by the number of values. 24/4 = 6

04 / COMMON TRAPS

Where students slip.

Trap

Forgetting to divide.

Fix

The sum is not the mean — divide by the count.

Trap

Dividing by the wrong count.

Fix

Divide by how many values there are.

05 / QUIZ

Test yourself.

The Test

12 problems across three tiers. Auto-graded on submit. Hints and a full walkthrough on every question. Your work is saved on this device — sign in to keep it across devices.

0/12Answered
How to answerType just the value. Formatting won't trip you up — we ignore spaces, capital letters, commas, and subscript style, so t₁ = 5, d = 3 and t1=5,d=3 both count. For a list of numbers, separate them with commas (e.g. 3, 10, 17).
Core

Core (4)

C1

Find the mean of: 5, 6, 2, 2, 8.

Need a hint?
  • Add every value.
  • Divide by how many there are.
C2

Find the mean of: 7, 11, 5, 8.

Need a hint?
  • Add every value.
  • Divide by how many there are.
C3

Find the mean of: 10, 3, 2, 12, 2.

Need a hint?
  • Add every value.
  • Divide by how many there are.
C4

Find the mean of: 10, 2, 4, 3, 2.

Need a hint?
  • Add every value.
  • Divide by how many there are.
Apply

Apply (4)

A1

Find the mean of: 10, 3, 8, 10, 6.

Need a hint?
  • Add every value.
  • Divide by how many there are.
A2

Find the mean of: 3, 10, 11, 7, 10.

Need a hint?
  • Add every value.
  • Divide by how many there are.
A3

Find the mean of: 8, 8, 7, 4, 10, 8.

Need a hint?
  • Add every value.
  • Divide by how many there are.
A4

Find the mean of: 11, 10, 11, 12, 3.

Need a hint?
  • Add every value.
  • Divide by how many there are.
Extension

Extension (4)

E1

Find the mean of: 9, 10, 9, 11.

Need a hint?
  • Add every value.
  • Divide by how many there are.
E2

Find the mean of: 7, 12, 5, 12.

Need a hint?
  • Add every value.
  • Divide by how many there are.
E3

Find the mean of: 4, 4, 8, 10.

Need a hint?
  • Add every value.
  • Divide by how many there are.
E4

Find the mean of: 3, 4, 12, 5, 3.

Need a hint?
  • Add every value.
  • Divide by how many there are.