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GLMPOWER Procedure


GLMPOWER Procedure

9.1  

The GLMPOWER procedure performs prospective analyses for linear models, with a variety of goals:

  • determining the sample size required to obtain a significant result with adequate probability (power)

  • characterizing the power of a study to detect a meaningful effect

  • conducting what-if analyses to assess sensitivity of the power or required sample size to other factors

You specify the design and the cell means using an exemplary data set, a data set of artificial values constructed to represent the intended sampling design and the surmised response means in the underlying population. You specify the model and contrasts using MODEL and CONTRAST statements similar to those in the GLM procedure. You specify the remaining parameters with the POWER statement, which is similar to analysis statements in the new POWER procedure.



KDE Procedure

9.1  

The new UNIVAR and BIVAR statements provide improved syntax. The BIVAR statement lists variables in the input data set for which bivariate kernel density estimates are to be computed. The UNIVAR statement lists variables in the input data set for which univariate kernel density estimates are to be computed.



LIFETEST Procedure

The new SURVIVAL statement enables you to create confidence bands (also known as simultaneous confidence intervals) for the survivor function S ( t ) and to specify a transformation for computing the confidence bands and the pointwise confidence intervals. It contains the following options.

  • The OUT= option names the output SAS data set that contains survival estimates as in the OUTSURV= option in the PROC LIFETEST statement.

  • The CONFTYPE= option specifies the transformation applied to S ( t ) to obtain the pointwise confidence intervals and the confidence bands. Four transforms are available: the arcsine-square root transform, the complementary log-log transform, the logarithmic transform, and the logit transform.

  • The CONFBAND= option specifies the confidence bands to add to the OUT= data set. You can choose the equal precision confidence bands (Nair 1984), or the Hall-Wellner bands (Hall and Wellner 1980), or both.

  • The BANDMAX= option specifies the maximum time for the confidence bands.

  • The BANDMIN= option specifies the minimum time for the confidence bands.

  • The STDERR option adds the column of standard error of the estimated survivor function to the OUT= data set.

  • The ALPHA= option sets the confidence level for pointwise confidence intervals as well as the confidence bands.

9.1  

The LIFETEST procedure now provides additional tests for comparing two or more samples of survival data, including the Tarone-Ware test, Peto-Peto test, modified Peto-Peto test, and the Fleming-Harrington G family of tests. Trend tests for ordered alternatives can be requested . Also available are stratified tests for comparing survival function while adjusting for prognostic factors that affect the event rates.



LOESS Procedure

9.1  

The LOESS procedure now performs DF computations using a sparse method when appropriate. In addition, the DFMETHOD=APPROX option is available.



LOGISTIC Procedure

The new SCORE statement enables you to score new data sets and compute fit statistics and ROC curves without refitting the model. Information for a fitted model can be saved to a SAS data set with the OUTMODEL= option, while the INMODEL= option inputs the model information required for the scoring.

The new STRATA statement enables you to perform conditional logistic regression on highly stratified data using the method of Gail, Lubin, and Rubenstein (1981). The OFFSET option is now enabled for logistic regression.

The LOGISTIC procedure now forms classification groups using the full formatted length of the CLASS variable levels.

Several new CLASS parameterizations are available: ordinal, orthogonal effect, orthogonal reference, and orthogonal ordinal.

You can now output the design matrix using the new OUTDESIGN= option.

The definition of concordance has been changed to make it more meaningful for ordinal models. The new definition is consistent with that used in previous releases for the binary response model.

9.1  

Enhancements for the exact computations include

  • improved performance

  • Monte Carlo method

  • mid- p confidence intervals

For an exact conditional analysis, specifying the STRATA statement performs an efficient stratified analysis. The method of Mehta, Patel, and Senchaudhuri (1992), which is more efficient than the Hirji, Tsiatis, and Mehta (1989) algorithm for many problems, is now available with the METHOD=NETWORK option.