This exercise requires the use of a computer package. A study on the effect of applying...

This exercise requires the use of a computer package. A study on the effect of applying fertilizer in bands is described in the article “Fertilizer Placement Effects on Growth, Yield, and Chemical Composition of Burley Tobacco” (Agronomy Journal [1984]: 183– 188). The accompanying data were taken from a scatterplot appearing in the article, with y = plant Mn (μg/g dry weight) and x = distance from the fertilizer band (cm). The authors suggest a quadratic regression model

a. Use a suitable computer package to find the estimated quadratic regression equation.

b. Perform the model utility test.

c. Interpret the values of R² and s_e. d. Are both the linear and quadratic predictors important? Carry out the necessary hypothesis tests and interpret the results.

e. Find a 90% confidence interval for the mean plant Mn for plants that are 30 cm from the fertilizer band.