Plan a statistical investigation
Theory
A statistical investigation answers a question using data. It has five steps: pose a question, collect data, organise it, display it, and write a conclusion. This Year 5 maths page shows how to plan each step so the answer can be trusted.
An investigation question must be answerable with data from many people or many trials, e.g. "How do students in our class travel to school?"
Data can come from a survey (asking people), an observation (watching and counting) or an experiment (doing something many times and recording what happens).
A biased question pushes people towards one answer ("Everyone loves pizza. What is your favourite food?"). Answer choices must be balanced and must not overlap.
Ask the right group: if the question is about the whole year group, ask students from every class. More data (more people, more days) gives a more reliable answer.
Use a column graph for categories and a dot plot for small whole-number counts. The conclusion answers the question using the numbers.
Choosing how to collect and display:
| Question type | Collect by | Display |
|---|---|---|
| Favourite sport of our class | Survey | Column graph |
| Cars passing the gate in 30 minutes | Observation | Column graph or table |
| How a paper cup lands when dropped | Experiment | Column graph |
| Number of pets each student has | Survey | Dot plot |
Planning an investigation
- Pose a clear question about a group.
- Decide what data you need and how to collect it (survey, observation or experiment).
- Write a fair question with balanced choices, and choose a fair sample.
- Organise the data in a table, display it in a suitable graph.
- Conclude: answer the question with the numbers, and say what could make it more reliable.
(i) How tall is the school flagpole?
(ii) Which fruit do students in our class most like?
(ii). It needs answers from many people. (i) needs one measurement.
Pose, collect, organise, display, conclude.
(i) The favourite game of students in 5K
(ii) The number of people in each car at drop-off
(iii) How often a toast lands butter side down
(i) Survey
(ii) Observation
(iii) Experiment
It tells people swimming is the most fun, so more people will choose it. Ask "Which is your favourite sport: ..." with a balanced list.
Ask students from every Year 5 class, or ask them all.
| \(8 + 11 + 5 + 3\) | \(=\) | \(27\) |
Most students in 5K travel by car: \(11\) of the \(27\) students. Walking is next with \(8\).
(i) Favourite colour (five colours)
(ii) Number of siblings, from \(0\) to \(5\)
(i) Column graph
(ii) Dot plot
Kai’s. With more days, one unusual day has less effect on the result.
Common pitfalls
Frequently asked questions
What are the steps of a statistical investigation?
Pose a question, collect data, organise it, display it and write a conclusion.
What is a biased question?
One that pushes people towards a particular answer.
When do you use an experiment?
When you need to do something many times and record what happens, like dropping a cup.
How can I make an investigation more reliable?
Collect more data, from a fair sample, over more than one day.
What should a conclusion include?
A direct answer to the question with numbers, e.g. "\(11\) of \(27\) students travel by car".