Frequency tables and frequency diagrams

When a lot of data 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 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.

13816121216
7181116157
111213211719
111410191312
7166141218

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, nTallyFrequency
5-10 \cancel{||||}~|6
11-15 \cancel{||||}~\cancel{||||}~||||14
16-20 \cancel{||||}~||||9
21-25 |1