Piecewise Constant Regression Analysis
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The GENMOD Procedure

        Model Information

Data Set              WORK.RATS_PW
Distribution               Poisson
Link Function                  Log
Dependent Variable           count
Offset Variable             loglen

Number of Observations Read         192
Number of Observations Used         192

        Class Level Information
 
Class        Value     Design Variables

interval     1          0      0      0
             2          1      0      0
             3          0      1      0
             4          0      0      1

trt          0          0              
             1          1              

           Parameter Information
 
Parameter       Effect       interval    trt

Prm1            Intercept                   
Prm2            interval     2              
Prm3            interval     3              
Prm4            interval     4              
Prm5            trt                      1  

           Criteria For Assessing Goodness Of Fit
 
Criterion                 DF           Value        Value/DF

Deviance                 187        266.3228          1.4242
Scaled Deviance          187        266.3228          1.4242
Pearson Chi-Square       187        241.2405          1.2901
Scaled Pearson X2        187        241.2405          1.2901
Log Likelihood                     -173.8752                

Algorithm converged.                                                       

                          Estimated Covariance Matrix
 
               Prm1           Prm2           Prm3           Prm4           Prm5

Prm1        0.02274       -0.02083       -0.02083       -0.02083      -0.006623
Prm2       -0.02083        0.03838        0.02083        0.02083      -1.05E-17
Prm3       -0.02083        0.02083        0.03778        0.02083      -1.18E-17
Prm4       -0.02083        0.02083        0.02083        0.04167      -6.81E-18
Prm5      -0.006623      -1.05E-17      -1.18E-17      -6.81E-18        0.02302

                       Analysis Of Parameter Estimates
 
                            Standard       Wald 95%          Chi-
Parameter     DF  Estimate     Error   Confidence Limits   Square  Pr > ChiSq

Intercept      1   -3.0882    0.1508   -3.3837   -2.7926   419.41      <.0001
interval   2   1    0.1719    0.1959   -0.2121    0.5558     0.77      0.3804
interval   3   1    0.2063    0.1944   -0.1746    0.5873     1.13      0.2885
interval   4   1   -0.0645    0.2041   -0.4646    0.3355     0.10      0.7519
trt        1   1   -0.8230    0.1517   -1.1204   -0.5257    29.43      <.0001
Scale          0    1.0000    0.0000    1.0000    1.0000                     

NOTE: The scale parameter was held fixed.