I wanted to understand the math behind the caluclation of Parameter Estimates in the following code. I wnat ot undertsand how the values of theta, scale and shape are computed in SAS, when we equate them to "est". It would be great if anyone could help me understand this. Code: data Plates; label Gap = 'Plate Gap in cm'; input Gap @@; datalines; -0.746 0.357 0.376 0.327 0.485 1.741 0.241 0.777 0.768 0.409 0.252 0.512 0.534 1.656 0.742 0.378 0.714 1.121 0.597 0.231 0.541 0.805 0.682 0.418 0.506 0.501 0.247 0.922 0.880 0.344 0.519 1.302 0.275 0.601 0.388 0.450 0.845 0.319 0.486 0.529 1.547 0.690 0.676 0.314 0.736 0.643 0.483 0.352 0.636 1.080 ; title 'Distribution of Plate Gaps'; ods output ParameterEstimates GoodnessOfFit FitQuantiles MyHist; proc univariate data=Plates; var Gap; histogram / midpoints=0.2 to 1.8 by 0.2 lognormal(theta=est sigma=est zeta=est) weibull (theta=est sigma=est c=est) gamma (theta=est sigma=est alpha=est) normal vaxis = axis1 name = 'MyHist'; inset n mean(5.3) std='Std Dev'(5.3) skewness(5.3) / pos = ne header = 'Summary Statistics'; axis1 label=(a=90 r=0); Thanks run;
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