An experiment was conducted to determine the effect of various levels of phosphorus on the inorganic phosphorus levels in a particular plant. The data in the table represent the levels of inorganic phosphorus in micromoles (mmol) per gram dry weight of Sudan grass roots grown in the greenhouse for 28 days, in the absence of zinc. Use the MINITAB output to answer the questions.

a. Plot the data. Do the data appear to exhibit a linear relationship?
b. Find the least-squares line relating the plant phosphorus levels y to the amount of phosphorus applied to the soil x. Graph the least-squares line as a check on your answer.
c. Do the data provide sufficient evidence to indicate that the amount of phosphorus present in the plant is linearly related to the amount of phosphorus applied to the soil?
d. Estimate the mean amount of phosphorus in the plant if .20 mmol of phosphorus is applied to the soil, in the absence of zinc. Use a 90% confidence interval.
MINITAB output for Exercise 12.62
Regression Analysis: y versus x
The regression equation is
y = 80.9 + 271 x

Transcribed Image Text:

Phosphorus Applied, x .50 μmol Phosphorus in Plant, y 204 195 247 245 25 μmol 159 127 95 144 .10 μmol 128 192 84 71 Predictor Constant Coef 80.85 SE Coef 22.40 68.31 3.61 3.96 0.005 0.003 270.82 S 39.04 19 R-Sq 61.1 R-Sq (adj) 57 .24 = predicted Values for New Observations New Obs 1 Fit 135.0 SE Pit 90 . 0 CI 90.0% p! 12.6 (112.1, 1579) (60.6, 209.4) Values of Predictors for New Observations New Obs 0.200