Normal probability plots are made to graphically verify normality assumption for data from a univariate population that are mutually independent and identically distributed. Normal probability plot is very common option in most statistical packages. In the context of design of experiments or regression, though the observations are assumed to be mutually independent and homoscedastic, they have different unknown expectations. So the raw data are inappropriate for normality check. To overcome the problem of unequal expectations, it is common to use residuals of a fitted regression model. The residuals have zero expectation, but these are heteroscedastic, and also mutually dependent. It is thus inappropriate to use the residuals for normality check. In this study, mutually independent homoscedastic components with zero mean are extracted from residuals through principle component analysis; these are then used for normal probability plot. The technique is illustrated with data.