Frequency distribution chart is a tabulation of values that one or more variables taken from a sample. A frequency distribution shows the number of observations falling into each of several ranges of values. Frequency distributions are portrayed as frequency tables, histograms, or polygons. Frequency distributions can show either the actual number of observations falling in each range or the percentage of observations. In the latter instance, the distribution is called a relative frequency distribution.
Uses and Properties of Frequency Distribution Chart:
A Frequency Distribution shows us a summarized grouping of data divided into mutually exclusive classes and the number of occurrences in a class. It is a way of showing unorganized data e.g. to show results of an election, income of people for a certain region, sales of a product within a certain period, student loan amounts of graduates, etc. Some of the graphs that can be used with frequency distributions are histograms, line graphs, bar charts and pie charts. Frequency distributions are used for both qualitative and quantitative data.
Managing and operating on frequency tabulated data is much simpler than operation on raw data. There are simple algorithms to calculate median, mean, standard deviation etc. from these tables.
A frequency distribution is said to be skewed when its mean and median are different. The kurtosis of a frequency distribution is the concentration of scores at the mean, or how peaked the distribution appears if depicted graphically–for example, in a histogram. If the distribution is more peaked than the normal distribution it is said to be leptokurtic; if less peaked it is said to be platykurtic.
Here is an example to create a frequency distribution chart for a given set of values.
Preparing Frequency Distribution Chart:
Consider the following set of data which are the high temperatures recorded for 30 consecutive days. Let us summarize this data by creating a frequency distribution chart of the temperatures.
Data Set – High Temperatures for 30 Days
50 45 49 50 43
49 50 49 45 49
47 47 44 52 51
44 47 46 50 44
51 49 42 43 49
45 46 45 51 46
Steps to create a frequency distribtion chart:
Step 1: Identify the highest and lowest values in the data set. For our temperatures the highest temperature is 52 and the lowest temperature is 42.
Step 2: Create a column with the title of the variable we are using, in this case temperature. Enter the highest score at the top, and include all values within the range from the highest score to the lowest score.
Step 3: Create a tally column to keep track of the scores as you enter them into the frequency distribution. Once the frequency distribution is completed you can omit this column. Most printed frequency distributions do not retain the tally column in their final form.
Step 4: Create a frequency column, with the frequency of each value, as show in the tally column, recorded.
Step 5: At the bottom of the frequency column record the total frequency for the distribution proceeded by N =
Step 6: Enter the name of the frequency distribution at the top of the table.