Frequency

Frequency is the number of times an item is counted in a dataset.

For example:

In the following the sample, the frequency of 2 is 3.

1 , 1 , 2 , 5 , 6 , 2 , 9 , 5 , 7 , 5 , 2 , 5 , 9 , 5

Count the number of times 2 appears.

Frequency is important for presenting data in tables or charts, and in calculating probability (relative frequency).

The value that occurs with the most frequency is the mode.

Mode

Mode is the value in a dataset that appears the most frequently.

For example:

In the following the sample, the mode is 5

1
1
2
5
6
2
9
5
7
5
2
5
9
5

Count the number of times 5 appears. It appears the most, so it is the mode.

Some datasets have more than one mode.

If there is a single mode, the term 'unimodal' is used. The example above is unimodal. There are five 5's. Had there also been five 2's, than the example is no longer unimodal. Then, both five and two would be called modes.

The mean, median, and mode are all measures of central tendency. The skew can be determined by comparing these three measures.