Histograms

Histograms

Is a graphical display of data using bars of different heights. It is similar to bar charts, but a Histogram groups numbers into ranges (intervals). And you decide what range to use.

Drawing Histograms from Frequency Distribution Table

For example; you measure the height of every tree in the orchard in Centimeters (cm) and notice that, their height vary from 100 cm to 340 cm. And you decide to put the data into groups of 50 cm. the results were like here below:

Height (cm)	Frequency
100 - 150	5
150 - 200	30
200 - 250	28
250 - 300	50
300 - 350	10

Represent the information above using a histogram.

Solution

Height (cm)	Class mark	Frequency
100 - 150	125	5
150 - 200	175	30
200 - 250	225	28
250 - 300	275	50
300 - 350	325	10
Total		123

**Scale:**vertical scale: 1 cm represents 5 trees horizontal scale: 1 cm represents 50 cm (range of trees heights).

Interpretation of Histograms

The histogram below represents scores achieved by 250 job applicants on a personality profile.

1. Percentage of the job applicants scored between 30 and 40 is 10%
2. Percentage of the job applicants scored below 60 is 90%
3. Job applicants scored between 10 and 30 is 100