Frequency Distributions and Graphs

Raw Data

Data collected in its original form.

Frequency Distribution

The organization of raw data in table form using classes and frequencies.

Class

A quantitative or qualitative category into which each raw data value is placed.

Frequency

The number of data values obtained in a specific class.

Three Types of Frequency Distributions

Categorical Frequency Distribution, Ungrouped Frequency Distribution, and Grouped Frequency Distribution.

Categorical Frequency Distribution

A frequency distribution used for data that can be placed in specific categories such as nominal level or ordinal level data.

Grouped Frequency Distribution

A frequency distribution used when the range of the data is large and the data must be grouped into classes that are more than one unit in width.

Open Ended Distribution

A frequency distribution with an open ended class.

Purpose of a Frequency Distribution

Enables the researcher to see the nature of the data more easily than by looking at the raw data especially when there are many data values.

Frequency Distribution Analysis

A frequency distribution is analyzed by looking for peaks and extreme values.

Peaks

Classes that have the most data values compared to the other classes.

Outliers

Extreme values that are unusually large or small relative to the other data values.

Class Boundaries or Exact Class Limits

The upper and lower values of a class for a grouped frequency distribution whose values have one additional decimal place more than the data and end in the digit 5.

Class Midpoint or Class Mark

A value for a class in a frequency distribution obtained by adding the lower and upper class boundaries or the lower and upper class limits and dividing by 2.

Cumulative Frequency

The sum of the frequencies accumulated up to the upper boundary of a class in a frequency distribution.

Relative Frequency

The quotient of the frequency of a class and the total number of values.

Cumulative Relative Frequency

The sum of the relative frequencies accumulated up to the upper boundary of a class in a frequency distribution.

Ungrouped Frequency Distribution

A frequency distribution used when the range of the data is relatively small and a single data value is used for each class