There are 12 Burr distributions. In many cases there are no published formulae for mean, variance, skewness or kurtosis. Although these might be developed, the majority of the distributions would offer a poor fit to process data that would almost certainly be bettered by other distributions for which the formulae exist. Indeed, they are largely neglected in the literature. The exception is Type XII, which we will show gives one of the best fits to the C4 in propane data.
21.1 Type I
The Burr‐I distribution is more commonly known as the uniform distribution, as described in Section 5.1.
21.2 Type II
The Burr‐II distribution is also known as the generalised logistic distribution, as described in the next chapter.
21.3 Type III
The Burr‐III distribution is described by the PDF
Figure 21.1 shows the effect of varying δ1 and δ2 with α fixed at 0 and β at 1. The CDF is
Fitting to the C4 in propane data gives α as −4.35, β as 3.84, δ1 as 4.86 and δ2 as 35.3. RSS is 0.0399.
The CDF can be inverted to give the QF.
21.4 Type IV
The Burr‐IV distribution is described by the PDF