Statistics: Frequency table

Definition of frequency table:

A collection of numerical facts about objects or events is called data. It is possible that some numerical values occur more than once in a set of data. The number of times each numerical value occurs in the set is called its frequency. It may be important to know the frequency of each numerical value in the data set. A convenient way to determine the frequency of each numerical value, is by constructing a frequency table, where in the frequency of each item in the data is written against the item in the form of a table. Such a table is also called a frequency distribution. An additional column of tally marks can also be made as that makes it convenient to determine the frequency of each item.

Frequency table examples:

Frequency tables can be made and used in various ways. For example, the test scores of a set of students can be put into a frequency table, where number of students against each total score becomes the frequency of that score. The blood sugar levels of patients in a hospital can be tabulated into a frequency table, which can help us understand the general health of the people in that area. The number of car accidents occurring on a particular highway over a period of time, can also be made into a frequency table example.

Relative frequency table:

If each of the frequency in the table is divided by the total frequency we get the relative frequency table.

Types of frequency distributions:

1. Ungrouped frequency table: When tabulation is done with respect to a discrete random variable, it is known as Discrete or ungrouped or simple frequency table. In this case the characteristic under consideration is a discrete variable and can assume only discrete values. For example, the frequency distribution of the number of babies born at a particular nursing home based on gender, would be a discrete or ungrouped frequency table. A baby born can be either a girl or a boy. The two groups cannot be combined. Also from above, the example of the number of accidents occurring on the highway would also be an ungrouped frequency distribution.

2. Grouped frequency table: In case the characteristics under consideration is a continuous variable, then it would be a grouped frequency table. In a grouped frequency table, the tabulation is done not against a single value, but against a group of values. For example, the weight of babies born at a particular nursing home would make a grouped frequency table.