Problem 1:
A services process is monitored using x and R charts. Eight samples of n = 10 observations
Have been gathered with the following results:
Sample Mean Range
1 4.2 .43
2 4.4 .52
3 3.6 .53
4 3.8 .20
5 4.9 .36
6 3.0 .42
7 4.2 .35
8 3.2 .42
a. Using the data in the table, compute the center line, the upper control limit, and the lower control limit for the x and R charts.
b. Is the process in control? Interpret the charts.
c. If the next sample results in the following values (2.5, 5.5, 4.6, 3.2, 4.6, 3.2, 4.0, 4.0, 3.6, 4.2), will the process be in control?
Problem 2: A product consists of 45 components. Each component has an average reliability of 97. What is the overall reliability for this product?
Problem 3: An inspector visually inspects 200 sheets of paper for aesthetics. Using trained judgment, the inspector will either accept or reject sheets based on whether they are flawless. Following are the results of recent inspections:
Sample 1 2 3 4 5 6 7 8 9 10
Defectives 10 15 12 14 26 3 10 14 12 11
a. Given these results, using a p chart, determine if the process is stable.
b. What would need to be done to improve the process?
Problem 4: You are to decide between three potential suppliers for an assembly for a product you are designing.
After performing life testing on several assembles, you find the following:
a. Given these results, using a p chart, determine if the process is stable.
b. What would need to be done to improve the process?
Problem 5: You are to decide between three potential suppliers for an assembly for a product you are designing.
After performing life testing on several assembles, you find the following:
Supplier MTBF (h) MTTR (h)
A 45 2
B 100 6
C 150 9
Based on system availability, which supplier would you use?