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(b) Use Excel’s multiple regression function to ﬁnd the relationship between
these variables and place it below the table.
(c) Use number format (2 decimal places) for the multiple correlation on the
Summary Output, and use number format (three decimal places) for the
coefﬁcients in the Summary Output.
(d) Print the table and regression results below the table so that they ﬁt onto
one page.
(e) By hand on this printout, circle and label:
(1a) multiple correlation R xy
(2b) coefﬁcients for the y-intercept, precipitation, and temperature.
(f) Save this ﬁle as: PLANT3A
(g) Now, go back to your Excel ﬁle and create a correlation matrix for these
three variables, and place it underneath the Summary Table. Change each
correlation to just two decimals. Save this ﬁle again as: PLANT3A
(h) Now, print out just this correlation matrix in portrait mode on a separate
sheet of paper.
1. What is the multiple correlation R xy ?
2. What is the y-intercept a?
3. What is the coefﬁcient for precipitation b 1 ?
4. What is the coefﬁcient for temperature b 2 ?
5. What is the multiple regression equation?
6. Underneath this regression equation by hand, predict the productivity you would
expect for an annual precipitation of 300 cm/year and an annual temperature of
+2 C.
Answer the following questions using your Excel printout. Be sure to include the
plus or minus sign for each correlation:
7. What is the correlation between precipitation and productivity?
8. What is the correlation between temperature and productivity?
9. What is the correlation between temperature and precipitation?
10. Discuss which of the two predictors is the better predictor of productivity.
11. Explain in words how much better the two predictor variables combined
predict productivity than the better single predictor by itself.
3. The Advanced Placement (AP) Tests are standardized tests that allow high
school students to ‘‘test out’’ of college courses, either by receiving credit for
these courses or by allowing the students to waive courses in which their AP
scores are very high. The AP Exams are scored on a 5-point scale in which a
score of ‘‘1’’ means ‘‘No recommendation’’ and a score of ‘‘5’’ means
‘‘Extremely well qualiﬁed.’’ There are 34 AP courses for which these exams
are available. The Biology Test is intended to measure the equivalent of a
college introductory biology course taken by Biology Majors during their ﬁrst-
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