A Researcher from the Crop and Soil Sciences Department at Your

Multiple Choice

A researcher from the crop and soil sciences department at your local university is interested in the relationship between the amount of phosphorus and nitrogen found in the ground. She takes a random sample of sites in the Commonwealth of Virginia and fits a linear regression model to the data. Based on this model, she obtains the following prediction results:
$$\begin{array} { | c | c | c | c | c | } \hline \text { Nitrogen Level } & \begin{array} { c } \text { Predicted } \\\text { Phosphorus Level }\end{array} & \begin{array} { c } \text { Std Error } \\\text { Predict }\end{array} & \mathbf { 9 5 . 0 \% } \text { CI } & \mathbf { 9 5 . 0 \% } \text { PI } \\\hline 20 & 15 & 1.25 & ( 12,18 ) & ( 10,20 ) \\\hline\end{array}$$ What is a 95% confidence interval for the mean amount of phosphorus when the nitrogen level is 20?

A) (12, 18)
B) (10, 20)
C) 15 ± 1.25
D) 15 ± 2.49