Stat 330 (Spring 2015): Homework 12

Stat 330 (Spring 2015): Homework 12
Due: May 1, 2015
Show all of your work, and please staple your assignment if you use more than one sheet. Write your name,
the course number and the section on every sheet. Show all work to earn partial credit. Problems marked
with * will be graded and one additional randomly chosen problem will be graded.
1. * A student interested in purchasing a multifunction inkjet printer wanted to study the relationship
between the retail price (in dollars) and the printing speed (pages per minute) of a typical personal
printer. He obtained data for 20 inkjet printers from a current PC magazine and calculated the following
n = 20
Σ x2i = 167.51
Σ xi = 56.3
Σ yi2 = 658528
Σ yi = 3232.0
Σ xi yi = 9918.3
(a) Estimate the linear regression equation predicting the price of an inkjet printer, y, based on the
printing speed, x.
(b) Predict the price in dollars for a printer with a speed of 3.5 pages a minute.
(c) Calculate the sample correlation between x and y and the coefficient of determination, R2 . What
does the R2 value tell you about the fit of your line?
(d) Provide an estimate of the error variance σ 2
2. * (Baron’s book): 9.10
3. * (Baron’s book): 9.16