Asking a statistical question
Plan a question that anticipates variation and define the data you need.
Before you begin
- Reading and recording measurements
- Recognising categories and numbers
Expect different values
A statistical question anticipates variation across observations. Asking the height of one named plant now seeks one measurement; asking how the heights of twenty seedlings vary seeks a distribution. Specify what will be measured, which group you are studying and when. A clear question makes it possible to decide whether the collected data actually answer it.
Plan consistent observations
Define the unit of observation and a measurement procedure before collecting data. For plant heights, use the same unit and measure from the same reference point. Record the number of observations and missing measurements honestly. A convenient set of plants may not represent every plant in a region, so limit your conclusion to the group and method your evidence supports.
Worked example
Improve the question 'Are journeys long?' so it can be investigated using numerical data.
Show the worked solution
- Define the group: students in one class on a specified school day.
- Define the measurement: journey duration in minutes, from leaving home to arriving at school.
- Ask how those durations vary and plan to record one observation per student using the same definition.
How do the school-journey times, in minutes, vary among students in this class on Monday?
Try it yourself
Which question is statistical?
Common mistakes
- A vague adjective such as large needs a measurable definition.
- A sample does not automatically represent a wider population.
What can you explain now?
Design a statistical question about seedlings and name the measurement unit, group and time.
Compare with the explanation
For example: How do the heights in centimetres of these 20 bean seedlings vary 14 days after planting?
This defines a varying numerical attribute, the group of twenty plants, the unit centimetres and the observation time. Other precise, investigable questions are valid.
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Original StudyForA content. AI-assisted checks completed; subject-teacher review is still pending. These lessons are not endorsed by an exam board.
Common Core mathematics standards ↗