Grouping data into class intervals Revision Card

AI generatedStatisticsKey Stage 3

Grouping data into class intervals.

Organise the data before calculating.
Check counts and totals, and keep units or context in your conclusion.
Choose a typical-value measure and a spread measure that suit the data.

Example 1

Group the data into width-5 classes starting at 0.

Tally each value into exactly one class

Class	Frequency
	3
	6
	0
Total	9

Black: given data. Blue: working we add.

Include the lower boundary and exclude the upper boundary. Do not count a boundary value twice.

The class frequencies are 3, 6, 0.

Example 2

Group the data into width-5 classes starting at 0.

Tally each value into exactly one class

Class	Frequency
	3
	5
	1
Total	9

Black: given data. Blue: working we add.

Include the lower boundary and exclude the upper boundary. Do not count a boundary value twice.

The class frequencies are 3, 5, 1.

Your turn

Question 1

Group the data into width-5 classes starting at 0.

Check answer

Tally each value into exactly one class

Class	Frequency
	2
	5
	2
Total	9

Black: given data. Blue: working we add.

Include the lower boundary and exclude the upper boundary. Do not count a boundary value twice.

The class frequencies are 2, 5, 2.

Question 2

Group the data into width-5 classes starting at 5.

Check answer

Tally each value into exactly one class

Class	Frequency
	6
	3
	0
Total	9

Black: given data. Blue: working we add.

Include the lower boundary and exclude the upper boundary. Do not count a boundary value twice.

The class frequencies are 6, 3, 0.

Question 3

Group the data into width-5 classes starting at 5.

Check answer

Tally each value into exactly one class

Class	Frequency
	6
	3
	0
Total	9

Black: given data. Blue: working we add.

Include the lower boundary and exclude the upper boundary. Do not count a boundary value twice.

The class frequencies are 6, 3, 0.

Question 4

Group the data into width-5 classes starting at 5.

Check answer

Tally each value into exactly one class

Class	Frequency
	3
	6
	0
Total	9

Black: given data. Blue: working we add.

Include the lower boundary and exclude the upper boundary. Do not count a boundary value twice.

The class frequencies are 3, 6, 0.

Question 5

Group the data into width-5 classes starting at 5.

Check answer

Tally each value into exactly one class

Class	Frequency
	3
	5
	1
Total	9

Black: given data. Blue: working we add.

Include the lower boundary and exclude the upper boundary. Do not count a boundary value twice.

The class frequencies are 3, 5, 1.