# Construction of a Histogram of a Continuous Grouped Frequency Distribution with Unequal Class Interval.

Procedure to Construct :-
1. Take a graph and draw two perpendicular lines. Mark them as OX and OY.

2. Take horizontal line OX as x-axis and vertical line OY as y-axis.

3. Choose suitable scale for class intervals on x-axis and represent class limits.

4. Choose a suitable scale along y-axis to represent frequencies.

5. Construct rectangle with class intervals as base and heights proportional to the frequencies

Example

Following are the ages of 180 patients getting medical treatment in a hospital on a day.

 Age (in years) 0-5 5-10 10-20 20-30 30-40 40-60 60-80 No of patients 25 25 20 30 20 40 20

Represent the above datas by histograms.

Solution

In this example the class intervals are not equal. The minimum class interval is 5-0 = 5. The maximum class size is 20. We shall find the adjustable frequency by the formula as follows.

Adjusted frequency of a class = × class frequency

Adjusted frequencies of the data will be :

 Age of (in years) No. of patients Adjusted frequency 0 - 5 25 × 25 = 25 5 - 10 25 × 25 = 25 10 - 20 20 × 20 = 10 20 - 30 30 × 30 = 15 30 - 40 20 × 20 = 10 40 - 60 40 × 40 = 10 60 - 80 20 × 20 = 5   