The upper limit is 11.69 + (.483)(.54) = 11.95
Chapter 3: Part IISolutions
James R. Martin, Ph.D., CMA
Professor Emeritus, University of South Florida
Chapter
3 Part II | MAAW's Textbook Table of Contents
Problem 3-9
1. d
2. a (c if 2 standard deviations are used to establish the limits.)
3. a
4. b
5. a
6. c
7. c
8. a
9. a
10. b
Problem 3-10
1. The grand mean is 11.69. The mean of the ranges is .54.
The values for the equation below are from Exhibit 3-9 and based on 6 items per sample.
The upper limit is 11.69 + (.483)(.54) = 11.95
The lower limit is 11.69 - (.483)(.54) = 11.429
2. The limits for the range are based on the following equations.
The upper limit is (2.004)(.54) = 1.08216
The lower limit is (0)(.54) = 0
3. Yes the process appears to be in control since all ten means are within the limits, although some of the individual observations are outside the limits.
Problem 3-11
The original grand mean is 129.6/12 = 10.8
The new grand mean is 120/12 = 10
Note that every point in the new set of data is below the original mean. Unless the truck is being used for a different purpose (e.g., city driving vs. highway, heavy loads vs. light loads), it appears that it might be time for a tune up. Another possibility is that a different type of gas is being used. A different driver who drives less economically could also cause different results.
