SAS Procedures

Help using Base SAS procedures
BookmarkSubscribeRSS Feed
🔒 This topic is solved and locked. Need further help from the community? Please sign in and ask a new question.
Piers_C
Calcite | Level 5

I have used PROC MIXED to fit a repeated measures spatial model to some spectrogram data (i.e. time-frequency representations). The datasets are quite large, 10800 data points. Following the advice stom Steve Denham in an earlier post, I checked the distribution of residuals. Despite looking like a very nice gaussian distribution, the skew is -0.016 and kurtosis 1.347. The Kolmogorov-Smirnov D test = 0.0185 Pr > D <0.0100. So, strictly speaking this distribution departs significantly from normal. I assume that the reason for this has more to do with the (relatively) large sample, and that I probably should not worry. Nevertheless, being a worrier i would really appreciate some advice.

 

Many thanks in advance

 

Piers_C

1 ACCEPTED SOLUTION

Accepted Solutions
Rick_SAS
SAS Super FREQ

As you say, the K-S test will reject for such as large sample. Clearly the residuals are symmetric, which is probably the most important feature. There is evidence of kurtosis, which could mean a heavier-tailed distribution of errors, but might also indicate slight heteroscedasity. 

 

Without seeing the data, this looks like a good fit. If these were my data, I would plot residuals versus explanatory variables. Do any of the patterns of residuals look "fan shaped"?

View solution in original post

1 REPLY 1
Rick_SAS
SAS Super FREQ

As you say, the K-S test will reject for such as large sample. Clearly the residuals are symmetric, which is probably the most important feature. There is evidence of kurtosis, which could mean a heavier-tailed distribution of errors, but might also indicate slight heteroscedasity. 

 

Without seeing the data, this looks like a good fit. If these were my data, I would plot residuals versus explanatory variables. Do any of the patterns of residuals look "fan shaped"?

sas-innovate-white.png

Join us for our biggest event of the year!

Four days of inspiring keynotes, product reveals, hands-on learning opportunities, deep-dive demos, and peer-led breakouts. Don't miss out, May 6-9, in Orlando, Florida.

 

View the full agenda.

Register now!

What is Bayesian Analysis?

Learn the difference between classical and Bayesian statistical approaches and see a few PROC examples to perform Bayesian analysis in this video.

Find more tutorials on the SAS Users YouTube channel.

SAS Training: Just a Click Away

 Ready to level-up your skills? Choose your own adventure.

Browse our catalog!

Discussion stats
  • 1 reply
  • 1082 views
  • 0 likes
  • 2 in conversation