Example 2. Example 2 considers the effect of changing the temporal variance on the 
shape of the CFD. Note that the population mean is held constant at 3 which corre¬ 
sponds to curve 2 of the preceding example. 
A-39 
Table 5.2. Parameter values and key for the family of curves shown in Figure 5.2 
A 
°s 
c 
color 
curve 
number 
~T~ 
~T~ 
1 
S 
Red 
~r 
1 
5 
Orange 
~T~ 
3 
1 
5 
Brown 
~T~ 
~T~ 
1 
5 
Green 
5 
~r 
5 
Blue 
5 
Figure 5.2. A family of curves illustrating the behavior of the CFD as the temporal popula¬ 
tion variance increases. The parameter values for each curve and the corresponding curve 
number are given in Table 5.2. Note that the curve 1 here has the same parameters as 
curve 2 in Figure 5.1. 
As temporal variance increases, the frequency of large proportions of space going 
out of compliance increases (Figure 5.2, lower right). Conversely, the frequency of 
small proportions of space out of compliance (i.e. large proportions of space being 
in compliance) decreases (Figure 5.2, upper left). That is, shifting the daily mean 
either down or up tends to shift the entire segment toward or away from compliance. 
appendix a 
The Cumulative Frequency Diagiam Method for Determining Water Quality Attainment 
