Numerical data that are normally distributed can be analyzed with parametric tests, that is tests which are based on the parameters that define a normal distribution curve. Parametric tests assume that: Data are numerical The distribution in the underlying population is normal Observations within a group are independent of one another The samples have been drawn randomly from the population The samples have the same variance (“homogeneity of variances”).
Normal distributions are shown via the bell curve, creating a uniform shape typically seen with large quantities of individuals participating in a study.