Various studies have linked alcohol dependence phenotypes to chromosome 4. One candidate gene is NACP (non-amyloid component of plaques), coding for alpha synuclein. Bo¨nsch et al. (2005) found longer alleles of NACP -REP1 in alcohol-dependent patients and report that the allele lengths show some association with levels of expressed alpha synuclein mRNA in alcohol-dependent subjects. The data are given in Table 14.1. Allele length is measured as a sum score built from additive dinucleotide repeat length and categorised into three groups: short (0− 4, n = 24), intermediate (5− 9, n = 58), and long (10− 12, n = 15). Here, we are interested in comparing the distribution of the expression level of alpha synuclein mRNA in three groups of subjects defined by the allele length. A global F -test in an ANOVA model answers the question if there is any difference in the distribution of the expression levels among allele length groups but additional effort is needed to identify the nature of these differences. Multiple comparison procedures, i.e., tests and confidence intervals for pairwise comparisons of allele length groups, may lead to additional insight into the dependence of expression levels and allele length.