Statistics · Mean

How to Find the Mean
Add All Values ÷ Count — 30 Practice Problems

Learn how to calculate the arithmetic mean (average) in 2 steps: add all values, divide by count. With 30 practice problems and mean vs median vs mode comparison.

⚡ RESPUESTA RÁPIDA

Mean = sum of all values ÷ count. For 4,7,13,2,9: sum=35, count=5. Mean=35÷5=7. The mean should always fall between the minimum and maximum values.

The Mean — What It Measures and When to Use It

Add all the values together4+7+13+2+9=35. Add every single data point — don't skip any.

Divide by how many values there areThere are 5 values. 35÷5=7. The mean is 7.

Verify — the mean should be between min and maxMin=2, Max=13. Is 7 between 2 and 13? Yes ✓. If the mean is outside this range, there's a calculation error.

Find missing value when you know the mean4 values with mean 8: total=8×4=32. Values are 5,9,10,x. x=32−(5+9+10)=32−24=8.

Mean vs Median vs Mode — When to Use Each

Measure	Best for	Avoid when
Mean	Symmetric data, test scores	Outliers present (salaries)
Median	Skewed data, income	Need exact mathematical average
Mode	Categories, sizes, surveys	All values are unique

30 Practice Problems

2,4,6,8,10

Mean=6

5,10,15,20

Mean=12.5

7,8,9,10,11

Mean=9

1,1,1,1

Mean=1

0,100

Mean=50

3,6,9

Mean=6

10,20,30,40,50

Mean=30

4,4,4,4,4

Mean=4

1,2,3,4,5,6

Mean=3.5

11,13,15,17

Mean=14

Mean=5, n=4, sum

20

Mean=8, vals 6,9,10,x

x=7

Scores 7,8,9,10,6

Mean=8

Temps 20,25,18,22

Mean=21.25

Ages 15,17,16,18,14

Mean=16

Weighted mean — when values have different importance

Exam 60% weight (score 75), homework 40% weight (score 90): mean=0.6×75+0.4×90=45+36=81. Not all averages are simple means.

Outliers distort the mean

5 people earn $20k each and 1 earns $200k. Mean=$53.3k — nobody earns that! Median=$20k is much more representative.

Can the mean be a decimal even with whole number data?

Yes. 1,2,3 has mean 2. But 1,2,4 has mean 7/3=2.333... The mean doesn't have to be one of the data values.

What's the difference between mean and average?

They're the same thing. 'Average' is the everyday word; 'mean' (specifically 'arithmetic mean') is the mathematical term. Both = sum÷count.

Does the mean change if I add the same number to all data?

If you add k to every value, the mean also increases by k. If you multiply all values by k, the mean also multiplies by k.

Also useful

Media,Mediana,Moda