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Tables, charts and diagrams
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Charts turn a table of numbers into a picture you can read at a glance. Choose the right chart for the data.
Types of data
Categorical data is in words: favourite colour.
Discrete numerical data can only take certain values: number of pets.
Continuous numerical data is measured and can take any value in a range: height, time.
Big sets of numbers are often grouped into classes such as 0 to 9, 10 to 19.
Discrete numerical data can only take certain values: number of pets.
Continuous numerical data is measured and can take any value in a range: height, time.
Big sets of numbers are often grouped into classes such as 0 to 9, 10 to 19.
Bar charts, pictograms and pie charts
Bar charts and pictograms suit categorical data. A pictogram needs a key, such as one symbol = 4 people.
Vertical line (or bar) charts suit numerical data.
In a pie chart the whole circle (360°) is the total. Angle = frequencytotal × 360°.
Vertical line (or bar) charts suit numerical data.
In a pie chart the whole circle (360°) is the total. Angle = frequencytotal × 360°.
Frequency tables
Frequency means how many. To find the mean from a frequency table, multiply each value by its frequency, add these up, then divide by the total frequency.
30 students choose a favourite sport. 8 choose tennis. What angle is the tennis sector of a pie chart?
- Each student gets 360° ÷ 30 = 12°
- 8 × 12°
Answer: 96°
Pick a chart that suits the data. In a pie chart, angle = frequency ÷ total × 360°. Mean from a table = total of (value × frequency) ÷ total frequency.
The interactive lesson includes the diagrams for this topic.
Check you have got it
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