ABSTRACT
The normal distribution is a key idea that shows up all over statistics. Most importantly, many statistical tests assume that variables are normally distributed, that is look like a normal distribution. The distribution in the histogram below is fairly close to normal by visual inspection, and a statistical test confirms it is sufficiently normal. Duchenne muscular dystrophy (DMD) is a disease which has as its hallmarks progressive muscle weakness and degeneration of skeletal muscle. This chapter provides an up-to-date review of this literature, and to report the preliminary results of a meta-analysis of the available data. Children with DMD have been reported to have Full-Scale intelligence quotients (FIQs) averaging around 80, or 1 standard deviation below the normal population intelligence quotient (IQ). There were 1146 individuals with DMD for whom the FIQ was available, and the distribution of their FIQ scores is showed. The mean FIQ of 80.2 was statistically different from the [general] population average FIQ of 100.
