Collect & organise data
Theory
To organise data, sort each result into a category and record it with a tally, then write the count for each category as its frequency. A crossed group of strokes stands for five.
Data is the set of results collected from a survey or an experiment.
Categorical data sorts each answer into a named group, such as a favourite sport. Numerical data is counted or measured numbers, such as a height in centimetres.
A tally records each result with a single stroke; every fifth stroke crosses the group of four, so the marks can be counted in fives.
The frequency of a category is the total number of strokes in its row.
Before you count, decide what kind of data a question collects.
| Question | Answer | Data type |
|---|---|---|
| Favourite sport? | Soccer, netball, ... | Categorical |
| Eye colour? | Brown, blue, ... | Categorical |
| How many pets? | \(0, 1, 2, ...\) | Numerical |
| Height in cm? | \(142, 150, ...\) | Numerical |
How to organise data with a tally
- List the categories down the first column of the table.
- Tally each result with a stroke in its row; cross every fifth stroke.
- Count the strokes in each row and write the total as the frequency.
- Check by adding all the frequencies — this is the number of results.
Count the crossed groups in fives, then the extras.
| \(5+5+4\) | \(=\) | \(14\) |
Add every frequency in the table.
| \(7+9+5+3\) | \(=\) | \(24\) |
Pick the largest frequency.
| \(12>6>5>2\) | Sunny |
A favourite fruit is a named group, so it is categorical. A height is a measured number.
The answer is favourite fruit.
Common pitfalls
Frequently asked questions
What is a tally?
A tally records each result with a single stroke. Every fifth stroke crosses the group of four, so the marks can be counted quickly in fives.
What is frequency?
The frequency of a category is how many results fall in it — the total number of tally strokes in that row.
What is the difference between categorical and numerical data?
Categorical data sorts answers into named groups, like favourite sport. Numerical data is counted or measured numbers, like the number of pets or a height in centimetres.
How do I find the total number of results?
Add every frequency in the table. Because each result is counted once, the sum of the frequencies is the number of results collected.
What makes a good survey question?
A good question is clear, offers choices that do not overlap and does not push the answer one way. Naming the categories lets every answer be tallied straight away.