Frequency tables and frequency diagrams
When a lot of dataValues, typically letters or numbers. needs to be sorted, one of the most efficient ways is to use a frequency table.
It is important to consider the sizes of groups when sorting data into a frequency tableThe total of the tally marks is called the frequency, which is shown in an addition column to the right. With this extra-column, the table is called a frequency table..
Example
Megan owns a bakery. She counts the number of customers she has at lunchtime each day on 30 consecutive days. These are the results.
| 13 | 8 | 16 | 12 | 12 | 16 |
| 7 | 18 | 11 | 16 | 15 | 7 |
| 11 | 12 | 13 | 21 | 17 | 19 |
| 11 | 14 | 10 | 19 | 13 | 12 |
| 7 | 16 | 6 | 14 | 12 | 18 |
| 13 |
| 8 |
| 16 |
| 12 |
| 12 |
| 16 |
| 7 |
| 18 |
| 11 |
| 16 |
| 15 |
| 7 |
| 11 |
| 12 |
| 13 |
| 21 |
| 17 |
| 19 |
| 11 |
| 14 |
| 10 |
| 19 |
| 13 |
| 12 |
| 7 |
| 16 |
| 6 |
| 14 |
| 12 |
| 18 |
It can be useful to put the data into groups to give an overview summary of the data. The smallest number is 6 and the biggest number is 21, so groups that have a width of 5 are reasonable. This will give four groups as shown below.
| Number of customers, \(n\) | Tally | Frequency |
| 5-10 | \(\cancel{||||}~|\) | 6 |
| 11-15 | \(\cancel{||||}~\cancel{||||}~||||\) | 14 |
| 16-20 | \(\cancel{||||}~||||\) | 9 |
| 21-25 | \(|\) | 1 |
| Number of customers, \(n\) | 5-10 |
|---|---|
| Tally | \(\cancel{||||}~|\) |
| Frequency | 6 |
| Number of customers, \(n\) | 11-15 |
|---|---|
| Tally | \(\cancel{||||}~\cancel{||||}~||||\) |
| Frequency | 14 |
| Number of customers, \(n\) | 16-20 |
|---|---|
| Tally | \(\cancel{||||}~||||\) |
| Frequency | 9 |
| Number of customers, \(n\) | 21-25 |
|---|---|
| Tally | \(|\) |
| Frequency | 1 |