Skip to main content

Table 3 Simulation results: estimations of bias and mean squared error for the Weibull model

From: Estimating time-to-onset of adverse drug reactions from spontaneous reporting databases

       Naive estimator   TBE
      λ ̂   β ̂   λ ̂   β ̂  
λ β p n BIAS MSE BIAS MSE BIAS MSE BIAS MSE NPM
0.05 0.5 0.25 100 4.04 16.7 0.200 0.044 0.465 0.51 0.046 0.007 312
    500 3.95 15.6 0.195 0.039 0.106 0.04 0.013 0.001 201
0.05 0.5 0.50 100 0.762 0.60 0.167 0.031 0.068 0.018 0.024 0.005 172
    500 0.747 0.56 0.164 0.028 0.015 0.003 0.003 0.001 22
0.05 0.5 0.80 100 0.160 0.027 0.119 0.017 0.008 0.002 0.009 0.004 9
    500 0.156 0.025 0.113 0.013 0.001 <0.001 0.001 <0.001 0
1 0.5 0.25 100 80.4 6612 0.201 0.044 8.68 183 0.046 0.007 300
    500 78.9 6249 0.194 0.038 2.07 17 0.012 0.001 186
1 0.5 0.50 100 15.0 233 0.174 0.034 1.53 7.99 0.031 0.006 163
    500 15.0 225 0.164 0.028 0.32 1.17 0.003 0.001 24
1 0.5 0.80 100 3.20 10.8 0.117 0.017 0.16 0.67 0.007 0.004 13
    500 3.15 10.0 0.112 0.013 0.041 0.15 <0.001 <0.001 0
0.05 2 0.25 100 0.121 0.015 0.354 0.16 <0.001 0.002 0.097 0.075 8
    500 0.120 0.014 0.333 0.12 -0.004 0.001 0.020 0.016 2
0.05 2 0.50 100 0.065 0.004 0.278 0.11 -0.004 <0.001 0.047 0.074 6
    500 0.064 0.004 0.264 0.08 -0.002 <0.001 0.004 0.016 0
0.05 2 0.80 100 0.032 0.001 0.182 0.063 <0.001 <0.001 0.046 0.063 1
    500 0.032 0.001 0.157 0.031 <0.001 <0.001 0.008 0.014 0
1 2 0.25 100 2.41 5.84 0.364 0.17 0.090 0.79 0.10 0.075 1
    500 2.41 5.79 0.336 0.12 -0.082 0.38 0.02 0.015 0
1 2 0.50 100 1.29 1.68 0.283 0.12 -0.073 0.33 0.052 0.069 3
    500 1.29 1.65 0.261 0.07 -0.065 0.12 -0.002 0.017 0
1 2 0.80 100 0.638 0.41 0.186 0.065 -0.024 0.086 0.045 0.064 0
    500 0.636 0.40 0.154 0.030 -0.007 0.014 0.004 0.013 0
  1. The mean squared error formula is MSE( λ ̂ )=Var( λ ̂ )+ ( BIAS ( λ ̂ ) ) 2 . Calculations were made on the replications where there was no problem of maximization. In the last column appear the number of problems of maximization for the truncation-based approach. There was no problem of maximization for the naive approach. Abbreviations : TBE truncation-based estimator, MSE mean squared error, NPM number of maximization problems.
\