Model	Number of parameters	Formula
Null	1	y = a
Full	No. of groups	y = group mean
Logistic	2	$\begin{array}{c}\hfill \mathrm{y}=\frac{1}{1+exp(-\mathrm{a}-\text{bx})}\end{array}$
Probit	2	$\mathrm{y}=\text{pnorm}((\mathrm{x}-\mathrm{a})·\mathrm{b})$
Log‐logistic	3	$\begin{array}{c}\hfill \mathrm{y}=\mathrm{a}+\frac{1-\mathrm{a}}{1+exp(\mathrm{c}·log(\frac{\mathrm{b}}{\mathrm{x}}))}\end{array}$
Log‐probit	3	$\mathrm{y}=\mathrm{a}+(1-\mathrm{a})·\text{pnorm}(\mathrm{c}·log(\frac{\mathrm{x}}{\mathrm{b}}))$
Weibull	3	$\mathrm{y}=\mathrm{a}+(1-\mathrm{a})(1-exp(-(\frac{\mathrm{x}}{\mathrm{b}}{)}^{\mathrm{c}}))$
Gamma	3	y = pgamma(bx; c)
Two‐stage	3	$\mathrm{y}=\mathrm{a}+(1-\mathrm{a})(1-exp(-\frac{\mathrm{x}}{\mathrm{b}}-\mathrm{c}(\frac{\mathrm{x}}{\mathrm{b}}{)}^2))$