| Models | Location (µ) | Scale (σ) | Shape (ξ) |
| Model 1 | constant | constant | constant |
| Model 2 | µ(t) = µ0 + µ1t | constant | constant |
| Model 3 | constant | σ(t) = σ0 + σ1t | constant |
| Model 4 | µ(t) = µ0 + µ1t | σ(t) = σ0 + σ1t | constant |