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ijhgo_uynrtpwiavnckml
‎04-05-2017
  • 2 Posts
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Can you run a Nonparametric ANCOVA?

by Calcite | Level 5 in SAS Studio
‎04-03-2017 02:59 AM
‎04-03-2017 02:59 AM
I am having an issue trying to find a way to code a nonparametric ANCOVA, and I am wondering if its even possible in SAS. I have 1 fixed effect and 1 covariate. The assumption of normality is met, however the assumption of homogeneity of errors is not met (p-value for fixed effect = 0.0432 using Levene's test). I have tried several transformations (log, ln, power, squareroot, arcsine squareroot, etc.) and have not been able to meet the assumptions. I was hoping to do a ranked analysis, however I have not been able to figure out how to code it. Any assistance would be greatly appreciated!   Cheers. ... View more

PROC MIXED with RANDOM fails to ESTIMATE Random Effect coefficients

by Calcite | Level 5 in Statistical Procedures
‎03-16-2017 06:03 PM
‎03-16-2017 06:03 PM
Can anyone provide me with some insight on why the random statement has an estimate of 0?   I have multiple data sets with the same issue (although the code runs just fine on others). The number of replicates ranges from 4 to 6 between the sets (most have 5) with 5 or more levels of treatment.  I am running a proc mixed model and using the random statement to control for replicate (and also to see if there is an effect). This is the output I get for the random section:   Covariance Parameter Estimates     Cov ParmEstimate   StandardError     Z Value     Pr > Z rep                                                             0                                 .                    .                 . Residual                                           0.000250                    0.000072             3.460      .0003   Are there any tips or tricks that would allow me to get an estimate in this section?   Any advice would be appreciated. ... View more
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