Number of observations
6000
4000
2000
0
0123456
Number of accidents in six years
Figure 8.2 H istogram from six-year accident data (data source: Burg, 1967, 1968)
100
80
60
40
20
Number of observations
0
64 67 70 73
Percentage yield
76
Figure 8.3 H istogram for percentage yield with four intervals (data source:H ill, 1975)
Observed Data and Graphical Representation 251