What are the Shapiro-Wilk and Kolmogorov-Smirnov tests of normality?
The prerequisite for most of the statistical test is normal data distribution. We use tests of normality to asses whether data are normally distributed or not. If the data are normally distributed, we use parametric tests. If data are not normally distributed, we use nonparametric tests. We can also use plots to assess data distribution.
We use the Shapiro-Wilk test when we have a small sample size (N smaller than 50) and Kolmogorov-Smirnov test when we have a large sample size (N greater than 50).