Normal Q-Q Plot
Q-Q plot, also called Quantile-Quantile plot, supports to check if the data plausibly comes from approximately theoretical distribution; in this instance, Normal Distribution. A Q-Q plot is a scatterplot shaped by plotting two sets of quantiles (points below which a certain proportion of the data falls) in contrast to one another. If both groups of quantiles came from a similar distribution, we must see the points creating a coarsely straight line. Provided a vector of data, the normal Q-Q plot plots the data in sorted order versus quantiles from a standard normal distribution.
The second assumption in linear regression was that all the predictor variables are normally distributed. If it is true, the residuals will also be normally distributed. Normal Q-Q is a plot between standardized residuals and theoretical quantiles. Visually, we can inspect whether the residuals follow the straight line, if it is normally distributed, or if there is any deviation that indicates violation...
