Question

Construct a histogram and then a frequency polygon for the following frequency distribution.

Class Interval	11-20	21-30	31-40	41-50	51-60	61-70
Frequency	15	28	50	35	20	12

Answer 1

1. Organize the data into equal intervals by subtracting 0.5 from lower limit of each class and add 0.5 to the upper limit of each class .

2. On the x-axis , take 1 cm as 5 units and plot class interval .

3. On the y-axis , take 1 cm as 5 units and plot frequency.

4. Draw rectangles of histogram as per given data.

5. For each rectangle , mark the midpoint of its length at the top part . In this case , points are (15.5,15),(25.5,28),(35.5,50),(45.5,35),(55.5,20),(65.5,12).

6. Mark two more midpoints of zero frequency on x-axis at the start and at the end .

7. Now connect the points using straight lines.

Class Interval	Frequency
10.5-20.5	15
20.5-30.5	28
30.5-40.5	50
40.5-50.5	35
50.5-60.5	20
60.5-70.5	12