Least squares mean changes in CDRS-R total score at week 8 were : -29.6 ( SE , 1.65 ) with quetiapine XR and -27.3 ( SE , 1.60 ) with placebo , a between-treatment group difference of -2.29 ( SE , 1.99 ; 95 % CI , -6.22 , 1.65 ; p = 0.25 ; mixed-model for repeated measures analysis ) .