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Type I error rates from 1000 simulations under the null hypothesis, β1=0, when individual-specific random coefficients have a normal distribution.
| Simulation parameters | Average number of cases | Type I error rates (%) | ||
|---|---|---|---|---|
| α | σ | CPa/FEb | GEEc | |
| −5 | 1 | 488 | 4.0 | 4.3 |
| 1.5 | 896 | 4.3 | 4.0 | |
| −6 | 1 | 179 | 3.7 | 4.0 |
| 1.5 | 336 | 5.0 | 5.1 | |
| −7 | 1 | 66 | 4.4 | 4.3 |
| 1.5 | 124 | 2.8 | 2.5 | |
| −8 | 1 | 25 | 6.2 | 6.0 |
| 1.5 | 46 | 4.1 | 4.0 | |
CP, conditional Poisson model.
FE, fixed effects model.
GEE, generalized estimation equations.
