The normal probability plot is a graph that plots the residuals against the expected value of that residual if it had come from a normal distribution. When the residuals are normally distributed or approximately so, the plot should appear as a straight line, sloping upward at a 45° angle.

Normal Probability Plot

A graphical technique for assessing whether or not a data set is approximately normally distributed, utilizing a plot of sorted values versus their expected values under normality.

Residuals

Differences between observed and predicted values of data in statistical models, indicating the error in predictions.

Normally Distributed

A statistical distribution depicting data that is evenly spread out across the mean, showing the predictable variability of values.