 # 6.3 Histograms with Class Interval of the Same Size

6.3 Histograms

(A) Draw a histogram based on the frequency table of a grouped data

1. A histogram is a graphical representation of a frequency distribution.
2. A histogram consists of vertical rectangular bars without any spacing between them.
3. Steps for drawing a histogram
(a) Determine the lower boundaries and upper boundaries for each class interval.
(b) Choose suitable scales for the horizontal axis (x-axis) to represent class interval and the vertical axis (y-axis) to represent frequency.

Example:
The following frequency table shows the radii, in cm, of different types of trees in a garden.

 Radii (cm) Frequency 2.0 – 2.4 7 2.5 – 2.9 5 3.0 – 3.4 10 3.5 – 3.9 2 4.0 – 4.4 6 4.5 – 4.9 4
Draw a histogram to represent the above information.

Solution:
 Radii (cm) Frequency Lower boundary Upper boundary 2.0 – 2.4 7 1.95 2.45 2.5 – 2.9 5 2.45 2.95 3.0 – 3.4 10 2.95 3.45 3.5 – 3.9 2 3.45 3.95 4.0 – 4.4 6 3.95 4.45 4.5 – 4.9 4 4.45 4.95