< List of probability distributions > *Fisher Z distribution*

The **Fisher Z distribution** (also called the *beta-logistic distribution*) is a four-parameter univariate and unimodal continuous distribution with infinite support. It can provide a better fit than the normal distribution for certain types of data, such as heat destruction of bacteria in food protection studies [1].

The Fisher Z distribution was first introduced by R. A. Fisher in 1924 [2]. It has been “rediscovered” since that date by many authors and goes by a variety of other names, including:

- Beta-prime exponential distribution,
- Exponential generalized beta prime distribution,
- Exponential generalized beta type II distribution,
- Generalized F distribution,
- Generalized Gompertz-Verhulst type II distribution,
- Generalized logistic type IV distribution,
- Log-F distribution,
- Prentice distribution.

## Fisher Z distribution properties

Although the Fisher Z distribution has many parameterizations of its probability density function (PDF), one of the most straightforward is [3]

Where

- ζ = location parameter,
- λ = scale parameter,
- α and γ = positive shape parameters α and γ (α, γ > 0),
- B( α, γ) = the beta function,
- x, ζ, λ, α, γ in ℝ.

When ζ = 0 and e λ = 1, the distribution is called the **standard Fisher Z distribution.**

An alternate parameterization given by [4] is

Prentice [5] also offers another parameterization of the distribution.

Special cases of the Fisher Z distribution include: Burr Type II distribution, Reversed Burr Type II distribution, logistic distribution, and hyperbolic secant distribution.

## References

[1] Kilsby, et al. Bacterial thermal death kinetics based on probability distributions: the heat destruction of Clostridium botulinum and Salmonella Bedford. J Food Prot 2000 Sep;63(9):1197-203. doi: 10.4315/0362-028x-63.9.1197

[2] Fisher, R. A. (1924). “On a Distribution Yielding the Error Functions of Several Well Known Statistics” (PDF). *Proceedings of the International Congress of Mathematics, Toronto*. **2**: 805–813.

[3] Crooks, G. (2019). Field Guide to Continuous Probability Distributions.

[4] Leo A. Aroian (December 1941). “A study of R. A. Fisher’s z distribution and the related F distribution”. The Annals of Mathematical Statistics. 12 (4): 429–448. doi:10.1214/aoms/1177731681. JSTOR 2235955.

[5] Prentice, R. L. (1975) *Discrimination among some parametric models*. Biometrika, 62(3):607-614.