Question

A researcher wanted to examine if soil type had any effects on the heights of daylilies (Y). The thickness of the soil (X) in the pot was used as the covariate X. Given the data that follow, where there are three types of soil (n = 10 in each group),

(a) calculate the adjusted mean values assuming that bw = 0.5,

and (b) determine what effects the adjustment had on the posttest results (describe effects of pre and post adjustment).

Soil Type	Height of daylilies (Y)		Thickness of soil
1	ȳ.₁ = 20		x̅.₁ = 21
2	ȳ .₂ =25		x̅.₂ =18
3	ȳ .₃ =30		x̅.₃ = 15

Answer 1