Question

What information can you get from a residuals plot that has a pattern rather than a random appearance?

Answer 1

Information depends upon the kind of pattern the residual plot is showing.

If the residual plot is random, it implies that the linear regression model is a good fit.

However, if the residual plot shows a pattern rather than a random appearance that implies a non-linear model will be a good fit for the data (rather than using a linear regression model). These non-linear models can include among others: squared, cubic, exponential, logarithmic regression models. An example of a non-random residual plot is shown below:

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