Graphics for Selecting a Probability Model

Statistical inferential techniques can be divided into two groups, namely parametric and non-parametric (distribution-free) techniques. The difference between the two types of procedures concerns the fact that in dealing with non-parametric techniques few assumptions are made regarding the nature of the distribution of the population from which the sample is drawn. Parametric procedures, on the other hand, are based on specific knowledge of the underlying probability distribution from which the sample derives. The level of significance in parametric testing and the confidence coefficient in parametric interval estimation are therefore valid only if the assumptions made in respect of the underlying probability distribution are actually correct.