Solution: Cramming One Thursday, researchers gave students

Chapter 9, Problem 25E

(choose chapter or problem)

Problem 25E

Cramming One Thursday, researchers gave students enrolled in a section of basic Spanish a set of 50 new vocabulary words to memorize. On Friday the students took a vocabulary test. When they returned to class the following Monday, they were retested—without advance warning. Here are the test scores for the 25 students.

Fri.	Mon.	Fri.	Mon.	Fri.	Mon.
42	36	48	37	39	41
44	44	43	41	46	32
45	46	45	32	37	36
48	38	47	44	40	31
44	40	50	47	41	32
43	38	34	34	48	39
41	37	38	31	37	31
35	31	43	40	36	41
43	32

a) What is the correlation between Friday and Monday scores?

b) What does a scatterplot show about the association between the scores?

c) What does it mean for a student to have a positive residual?

d) What would you predict about a student whose Friday score was one standard deviation below average?

e) Write the equation of the regression line.

f) Predict the Monday score of a student who earned a 40 on Friday.