Preface to First Edition - lib

112 SIMPLE AND MULTIPLE LINEAR REGRESSIONThe plot suggests that for smaller S-Ne values, seeding produces greaterrainfall than no seeding, whereas for larger values of S-Ne it tends to produceless. The cross-over occurs at an S-Ne value of approximately four whichsuggests that seeding is best carried out when S-Ne is less than four. Butthe number of observations is small and we should perhaps now consider theinfluence of any outlying observations on these results.In order to investigate the quality of the model fit, we need access to theresiduals and the fitted values. The residuals can be found by the residualsmethod and the fitted values of the response from the fitted (or predict)methodR> clouds_resid clouds_fitted