1. Histograms August, 2018
A histogram is used instead of a bar chart when the bars have unequal width.
This helps to give the graph a more realistic visual impression.

2. Time Fish 0 ≤ t < 1 4 1 ≤ t < 5 3 5 ≤ t < 7
An angler keeps a record of the number of fish caught. The angler puts this information onto a bar chart.

3. Why is the bar chart misleading?
Time
Fish
0 ≤ t < 1 4
1 ≤ t < 5 3
5 ≤ t < 7 6 5 4 3 2 1
Fish Caught 1 2 3 4 5 6 7 8 9
Time (Hours)

4. Fish Caught The areas of the bars give a false impression Time Fish4
1 ≤ t < 5 3
5 ≤ t < 7 6 5 4 3 2 1
To avoid this problem a histogram is used
Fish Caught 1 2 3 4 5 6 7 8 9
Time (Hours)

5. Time Fish Freq ÷ Width = FD 0 ≤ t < 1 4 4 ÷ 1 1 ≤ t < 5 3 3 ÷ 4
5 ≤ t < 7
4 ÷ 2 2 4 3 2 1
Frequency Density of Fish Caught 1 2 3 4 5 6 7 8 9
Time (Hours)

6. F W FD Frequency = Freq. Density x Class Width
Freq. Density = Frequency ÷ Width
Width = Frequency ÷ Freq. Density
Time
Fish
0 ≤ t < 2 8
2 ≤ t < 6 4
6 ≤ t < 7 10
Here are the results for another angler’s fishing catch F W
Calculate the frequency densities for the data in this table and draw a histogram for the data FD