Hi Reeza, So, basically there was a larger dataset initially, random samples were taken from that larger datasets. This random sample has 70 people. I want to compare features from these 70 people with features from the observations that weren't randomly selected (n=472) to assess representativeness. Does that make more sense? Thanks. ... View more

Thank you for walking through the problem with me! ... View more

Hi Steve, I just ended up using "ci=resampling" and I stopped getting those warning messages. The reason why I decided to use that is that when I did a multivariable model, SAS automatically used that option to calculate the confidence intervals. Do you think my reasoning is justifiable? ... View more

I'm getting these warning messages: "WARNING: The test for equal coefficients across quantiles is ignored because the joint covariance is not computed. WARNING: Heterogeneous covariance estimate is degenerate. Covariance and correlation for QUANTILE= 0.1 cannot be computed. WARNING: Heterogeneous covariance estimate is degenerate.   Covariance and correlation for QUANTILE= 0.9 cannot be computed. WARNING: Heterogeneous covariance estimate is degenerate. Covariance and correlation for QUANTILE= 0.99 cannot be computed. WARNING: The Wald test is ignored because the covariance could not be computed at QUANTILE= 0.1. WARNING: The Wald test is ignored because the covariance could not be computed at QUANTILE= 0.9. WARNING: The Wald test is ignored because the covariance could not be computed at QUANTILE= 0.99. WARNING: The likelihood ratio test is ignored at QUANTILE= 0.99 because the estimated sparsity function is close to 0." Should I be worried? I assume it's because there are no observations at certain percentiles. Is my understanding correct? Thanks. ... View more

Hi Steve, Thank you for your response. I have a very small sample size (n=70). I thought that using the ci=resampling option is unstable for small datasets. Is this incorrect? Thanks. ... View more

graphics on; quantreg algorithm=simplex; model x=y / quantile= .1 .2 .25 .3 .4 .5 .6 .7 .75 .8 .9 .99; run; ods graphics off;  run; ... View more

I can see how it could cause that...but I'm not sure what else to do. Because for those observations not enough biological sample was obtained for a proper measurement to be taken. ... View more

In my case zero just means that the value was actually zero. Values that were too small to be measured were treated as missing data. ... View more

Thanks Reeza jan, I didn't realize a few hours ago that this was a conventional way of solving the problem ... View more