Organising data & statistical charts · Ages 12–13
Kinds of data
Counted is discrete, measured is continuous.
How to do it
Method
Counted is discrete, measured is continuous
Number of people: discrete; height: continuous; colour: qualitative
Another way
A value in between?
150.5 lies between 150 and 151: continuous
In full
Data come in two kinds: qualitative data are categories, such as a colour or a favourite sport; quantitative data are numbers. Quantitative data are of two kinds again. Discrete data are counted and take separate values only: a number of people, of books, a shoe size. Continuous data are measured and can take any value in a range: a height, a weight, a time. One test: was it counted or measured? Counted is discrete, measured continuous. Another: is there a possible value between two values? Between 150 cm and 151 cm there is 150.5 cm, so height is continuous; between 3 people and 4 there is no 3.5 people, so a number of people is discrete. Continuous data are recorded as approximations: a height measured to the nearest cm and recorded as 150 cm is really from 149.5 cm up to 150.5 cm (not including 150.5 cm).
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
Weights are measured to the nearest kg. A weight recorded as 66 kg is really at least kg.
Show the answer and working
Answer: 65.5
Weight is continuous, rounded to the nearest kg before it is recorded, so it may really be up to 0.5 kg less: 66 − 0.5 = 65.5.
Example 2
The number of children in a family can be 5.
True or false?
Show the answer and working
Answer: True
A number of children is counted, discrete data: only whole numbers 0, 1, 2, 3…, never half a child.
Example 3
A 100 m time is measured to the nearest 0.1 s and recorded as 15.7 s. The real time is from s up to s (not including the second).
Fill in each blank
Show the answer and working
Answer: 15.65, 15.75
To the nearest 0.1 s, the real time is within 0.05 s of the record: 15.7 − 0.05 = 15.65, 15.7 + 0.05 = 15.75.
Practice questions to try
Try these 5; the answers are at the end. For a whole worksheet, see VIP worksheets below.
1.Tsz-ching records these over a week. Which one is discrete data?
- A. Amount of water drunk each day
- B. Temperature at noon each day
- C. Number of messages received each day
- D. Time spent asleep each day
Choose the right answer
Answer:
2.Tsz-ching writes a questionnaire. Which of these collects qualitative data?
- A. Favourite fruit
- B. Time spent exercising each day
- C. Weight of a backpack
- D. Number of televisions at home
Choose the right answer
Answer:
3.The number of children in a family can be 2.5.
True or false?
Answer:
4.Heights are measured to the nearest cm. A player recorded as 160 cm could really be 159.8 cm tall.
True or false?
Answer:
5.A 100 m time is measured to the nearest 0.1 s and recorded as 16.3 s. The real time is from s up to s (not including the second).
Fill in each blank
Answer:
All the answers
- 1. C. Number of messages received each day
- 2. A. Favourite fruit
- 3. False
- 4. True
- 5. 16.25, 16.35
VIP practice notes and papers
Aimed at tests and exams: questions on this topic, new every time, to print or save as a PDF.
- Practice notes: The key point, worked examples step by step, then questions of the same kind to follow, hints fading
- Practice paper: Set out in parts like a school paper, marked, with answers and full working
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