Example 1
A table shows class scores of 4, 7, 9, 10 and 12. Find the range.
- The largest value is 12.
- The smallest value is 4.
- Range = largest − smallest = 12 − 4
So: The range is 8.
Back to National 3
Topic
Tables and Graphs
Statistics is about reading data and using it to answer questions. You will use tables, tally charts, bar charts, pictograms, simple line graphs, range, and simple averages.
Topic explanation
Tables and tally charts organise values. Read the row or column label first so you use the correct numbers.
Bar charts and pictograms compare categories. Use the scale or key before deciding which value is biggest or smallest.
Line graphs show change over time. Describe the pattern using simple words such as rising, falling, same, highest or lowest.
Range and averages help summarise data. Always write a short statement in context after a calculation.
Data examples
Bar chart: club choices
Football
Dance
Art
Games
Football is the most popular. The difference between football and games is 8 - 3 = 5.
Pictogram: fruit choices
Key: one dot means 2 pupils.
Apples
Bananas
Grapes
Grapes has 5 dots. 5 × 2 = 10 pupils.
Tally and frequency table
| Pet | Tally | Frequency |
|---|---|---|
| Dog | |||| | | 6 |
| Cat | |||| | 4 |
| Fish | || | 2 |
Count each tally group. The total is 6 + 4 + 2 = 12.
Simple line graph
Follow the line from left to right. This one goes up, so the savings increased.
What to look for
Read the title, labels, scale and key before answering.
Watch out
Check what one picture is worth before counting the pictures.
Useful statements
The most popular choice is..., more pupils chose..., and the graph shows an increase.
Quick methods
- Read a chart
- Check the title, labels and scale before answering.
- Compare values
- Find the two values, then subtract or say which is bigger.
- Mean
- Add the values, then divide by how many there are.
- Range
- Subtract the smallest value from the largest value.
Worked examples
Example 2
A bar chart shows 6, 8, 10 and 12 pupils chose four activities. Find the mean number of pupils.
- Add the values: 6 + 8 + 10 + 12 = 36
- There are 4 values.
- Divide by 4: 36 divided by 4 = 9
So: The mean is 9.
Example 3
A pictogram key says one picture means 2 pupils. There are 5 pictures for football. How many pupils chose football?
- Read the key first.
- One picture means 2 pupils.
- 5 pictures means 5 × 2 = 10 pupils
So: 10 pupils chose football.