Parametric statisticsParametric inferential statistical methods
are mathematical procedures for statistical hypothesis testing
which assume that the distributions of the variables being assessed have certain characteristics. Analysis of variance
assumes that the underlying distributions are normally
distributed and that the variances
of the distributions being compared are similar. The Pearson product-moment correlation coefficient
While parametric techniques are robust – that is, they often retain considerable power to detect differences or similarities even when these assumptions are violated – some distributions violate the assumptions so markedly that a non-parametric alternative is more likely to detect a difference or similarity.