The following data resulted from an experiment to assess the potential of unburnt colliery spoil as a medium for plant growth. The variables are x 5 acid extractable cations and y = exchangeable acidity/total cation exchange capacity ("Exchangeable Acidity in Unburnt Colliery Spoil," Nature, 1969: 161):

Standardizing the independent variable x to obtain x' = (x - x̅)/sx and fitting the regression function y = β0* + β1* x'1 β2* (x')2 yielded the accompanying computer output.

a. Estimate µY.50.
b. Compute the value of the coefficient of multiple determination.
c. What is the estimated regression function β̂0 + β̂1x1 β̂2x2 using the unstandardized variable x?
d. What is the estimated standard deviation of β̂2 computed in part (c)?
e. Carry out a test using the standardized estimates to decide whether the quadratic term should be retained in the model. Repeat using the unstandardized estimates. Do your conclusions differ?

r-23 y 1.50 .46 32 1.17 .96 .78 77 x 58 67 81 96 100 113 y.9.78 69.5248.5.5 5 16 26 30 38 52 Parameter Estimate 8733 -.3255 0448 Estimated SD 0421 0316 0319