We can also calculate residuals as percentage error:
It is crucial to examine the residuals after a fit. When a fit is ``good,'' the residuals are non-uniformly distributed around the zero axis; that is, they appear to be random in magnitude and sign. A substantial or systematic deviation from the zero axis indicates some phenomenon is not being modeled or fitted correctly. An iterative process of fitting loglets to a data set and then examining the residuals is a good way to proceed, unless the errors in the data and shown in the residuals are known to come from other sources (e.g., a recession).
Loglet Lab provides views of both percentage and raw error.