Dataset: deadseaminerals.csv Source: Z. Ma'Or, S. Yehuda, and W. Voss (1997). "Skin Smoothing Effects of Dead sea Minerals: Comparative Profilometric Evaluation of Skin Surface," International Journal of Cosmetic Science, Vol. 19, pp.105-110. Description: Analysis of Covariance comparing 3 treatments (pre/post) with response being skin roughness (lower scores are better). Treatments 1=Gel Formulation, 2=Gel+1% Dead Sea Concentrate, 3=Placebo Data generated to match means SDs, mins, maxs, correlations. Variable Names: trt_Grp pre_x (baseline score) post_y (4 weeks post trt score) gel (Dummy variable for gel trt) gelDS (Dummy variable for gel + Dead Sea Concentrate trt)