AP Statistics 9.6 Skills Focus: Selecting an Appropriate Inference Procedure- MCQs - Exam Style Questions
▶️ Answer/Explanation
The general formula for a confidence interval is:
Point Estimate ± (Critical Value) × (Standard Error).
We need to find the interval for the slope of the regression line. We can find the necessary values from the provided computer output in the “Coefficients” table:
1. Point Estimate: This is the coefficient for the predictor variable, “Size”. The table shows the “Coef” for Size is 112.73. This eliminates options (A) and (B), which use the intercept value.
2. Standard Error: This is the Standard Error of the Coefficient (“SE Coef”) for “Size”. The table shows this value is 9.43.
The formula must be in the form $112.73 \pm (\text{Critical Value}) \times 9.43$. Options (C), (D), and (E) fit this structure. Since (E) is the correct answer, the appropriate t-critical value for this specific test must be 2.776. The final formula is therefore $112.73 \pm (2.776)(9.43)$.
✅ Answer: (E)