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(e) Save this ﬁle as: GRE12

Answer the following questions using your Excel printout:

1. What is the multiple correlation
R
xy
?

2. What is the y-intercept
a
?

3. What is the coefﬁcient for GRE VERBAL
b
1
?

4. What is the coefﬁcient for GRE QUANTITATIVE
b
2
?

5. What is the coefﬁcient for GRE WRITING b
3
?

6. What is the coefﬁcient for GRE BIOLOGY b
4
?

7. What is the multiple regression equation?

8. Predict the FIRST-YEAR GPA you would expect for a GRE VERBAL

score of 610, a GRE QUANTITATIVE score of 550, a GRE WRITING

score of 3, and a GRE BIOLOGY score of 610.

(f) Now, go back to your Excel ﬁle and create a
correlation matrix
for these ﬁve

variables, and place it underneath the SUMMARY OUTPUT.

(g) Save this ﬁle as: GRE13

(h) Now, print out
just this correlation matrix
on a separate sheet of paper.

Answer the following questions using your Excel printout. Be sure to

include the plus or minus sign for each correlation:

9. What is the correlation GRE VERBAL and FIRST-YEAR GPA?

10. What is the correlation between GRE QUANTITATIVE and

FIRSTYEAR GPA?

11. What is the correlation between GRE WRITING and FIRST-YEAR

GPA?

12. What is the correlation between GRE BIOLOGY and FIRST-YEAR

GPA?

13. What is the correlation between GRE WRITING and GRE VERBAL?

14. What is the correlation between GRE VERBAL and GRE BIOLGY?

15. Discuss which of the four predictors is the best predictor of

FIRSTYEAR GPA.

16. Explain in words how much better the four predictor variables together

predict FIRST-YEAR GPA than the best single predictor by itself.

2. In order to grow properly, most plants need water, warmth, carbon dioxide gas,

light, and minerals. Suppose you wanted to study the relationship between

temperature and precipitation and their effect on plant productivity. In

ecological terms, “productivity” refers to the amount of plant growth and it is measured

in grams per meter squared per year (g/m
2
/year) at the site. Precipitation

(rainfall) is measured as the annual mean precipitation (cm/year) at the site.

Temperature is measured as the average annual temperature in degrees

Centigrade (
o
C) at the site. Let productivity be the dependent variable (criterion), and

precipitation and temperature be the independent variables (predictors) at each

site. Hypothetical data for 14 sites are presented in Fig.
7.11
.

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