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6.1 Identifying data

6.1 Identifying data

When you carry out a statistical investigation, the "rst thing you need to do is decide on a hypothesis.
A hypothesis is a statement that you think may be true. It is not the same as a question.
A hypothesis must be written so that it is either ‘true’ or ‘false’.
Here are some examples of hypothesis statements.

Girls take care of their health better than boys do.

More people go to work by bus than by any other form of transport.
Using fertiliser on my tomato plants makes them grow bigger.

When you carry out a statistical investigation, you need to plan it "rst. Here is a suggestion for a plan.

1. Decide on a hypothesis to test.
For example: ‘13-year-old girls, on average, are taller than 13-year-old boys.’
2. Decide on the question, or questions, to ask.
For example: ‘Are you 13 years old?’, ‘Are you a girl or a boy?’ and ‘How tall are you?’

3. Decide what data to collect.
For example: The heights of 13-year-old girls and boys.

4. Decide how to collect the data.
For example: Carry out a survey of Stage 9 students.
5. Decide how big the sample size will be.
For example: 10% of the number of Stage 9 students (half boys, half girls).
6. Decide how accurate the data needs to be.
For example: Heights measured to the nearest centimetre.

Worked example 6.1

a Aiden lives in the UK. He is investigating which month of the year is the coldest.
Write a hypothesis for this investigation.
b Fran is investigating who is healthier, the males or the females in her village.
i Write down examples for each of the six steps suggested above.
ii What other factors could Fran consider?
iii Write down some problems Fran might have in collecting her data.

a ‘December is the coldest month of the year.’ Aiden could choose any of the winter months, so this
would be a suitable hypothesis.
b i 1 Hypothesis: ‘Males are healthier than females in my village’.
2 Questions: ‘Are you male or female?’, ‘What is your height?’,
‘How much do you weigh?’, ‘How many hours of exercise do you do each week?’
3 Data to collect: Heights and masses of adults so that Body Mass Index can be calculated.
Amount of exercise adults do so that comparisons can be made.

56 6 Planning and collecting data