why is random effects variable negative why is sas random effect negative what model returns a negative variance for each random effect why does sas return a negative variance why does a random variable return a negative variance why does sas return a negative variance why does sas return a negative variance for a random effect why is variance of sas negative why is sas negative for random effect why does sas output a negative variance does sas always return a negative variance why does random variable variance have a negative value why does the variance of randomness in statistics (sas) have to be larger than overall variability? why does sas return a negative variance? why does random effect return a positive variance why sas returns a negative variance why does sas return a negative variance sas returns a negative variance for a random effect why does sas return a negative variance why do random effect models return negative variance?