QUESTION $2$

$[$Total marks$=32]$

Consider the Phosphorus Data $($Cochran$,1967)$ from an investigation of the source from which corn plants obtain their phosphorus was carried out. Concentrations of phosphorus in parts per millions in each of $18$ soils were measured. The variables are: $x_1$ the concentrations of inorganic phosphorus in the soil, $x_2$ the concentrations of organic phosphorus in the soil, and $Y$ the phosphorus content of corn grown in the soil at $20C.$

Table $2\mathrm{.}1$ shows the residuals $(hat(lon{)}_i),$ the variance of each residual $(Var(hat(lon{)}_i)),$ the diagonal elements of the hat matrix $(h_{ii}),$ the studentized residuals $(t_i^{**}),$ the studentized deleted residuals $(t_i),$ the Cook's

$2$

STA$4804/013/0/2024$

distance $(D_i)$ and the difference in fit$($s$),($DFFITS$)$