Overhead Door (OD) Corporation’s founder, C. G. Johnson, invented the upward-lifting garage door in 1921 and the electric garage door opener in 1926. Since then OD has been a leading supplier of commercial, industrial, and residential garage doors sold through a nationwide network of more than 450 authorized distributors. They have built a solid reputation as a premier door supplier, commanding 15 % share of the market. Suppose that customers assess door quality first in terms of the ease of operation, followed by its durability. The quality improvement team (QIT) might then assign an engineering team to determine the factors that contribute to these two main problems. Smooth operation of a garage door is a critical quality characteristic that affects both problems: If a door is too heavy, it’s difficult and unsafe to balance and operate; if it’s too light, it tends to buckle and break down frequently or may not close properly. Suppose the design engineers determine that a standard garage door should weigh a minimum of 77.5 kg. and a maximum of 82.5 kg., which thus specifies its design quality specification. To determine the quality of conformance, suppose the QIT decides to collect data on the actual weights of 90 standard garage doors sampled randomly from their monthly production of almost 2,000 doors. See the tables on the next page. What is the sample mean over all 90 doors? What is the sample standard deviation? You can use an Excel function STDEV.S() to evaluate the sample standard deviation. Is there evidence to support the claim that a standard garage door weigh 80 kg.? What is the P-value? Use α = 0.01 What is the 99% confidence interval? Table 2: T\D 1 2 3 4 5 6 7 8 9 10 9 81 82 80 74 75 81 83 86 88 82 1 73 77 83 81 76 76 82 83 79 84 5 85 78 76 81 82 83 76 82 86 79 T\D 11 12 13 14 15 16 17 18 19 20 9 80 78 84 75 84 78 77 79 84 84 1 80 84 82 83 75 81 78 85 85 80 5 76 76 78 72 84 76 74 85 82 79 T\D 21 22 23 24 25 26 27 28 29 30 9 84 83 79 86 85 82 76 85 84 80 1 81 78 83 80 81 83 83 82 83 80 5 81 80 83 79 78 84 79 77 82 83
Overhead Door (OD) Corporation’s founder, C. G. Johnson, invented the upward-lifting garage door in 1921 and the electric garage door opener in 1926. Since then OD has been a leading supplier of commercial, industrial, and residential garage doors sold through a nationwide network of more than 450 authorized distributors. They have built a solid reputation as a premier door supplier, commanding 15 % share of the market.
Suppose that customers assess door quality first in terms of the ease of operation, followed by its durability. The quality improvement team (QIT) might then assign an engineering team to determine the factors that contribute to these two main problems.
Smooth operation of a garage door is a critical quality characteristic that affects both problems: If a door is too heavy, it’s difficult and unsafe to balance and operate; if it’s too light, it tends to buckle and break down frequently or may not close properly.
Suppose the design engineers determine that a standard garage door should weigh a minimum of 77.5 kg. and a maximum of 82.5 kg., which thus specifies its design quality specification. To determine the quality of conformance, suppose the QIT decides to collect data on the actual weights of 90 standard garage doors sampled randomly from their monthly production of almost 2,000 doors. See the tables on the next page.
What is the sample mean over all 90 doors? What is the sample standard deviation? You can use an Excel
Is there evidence to support the claim that a standard garage door weigh 80 kg.? What is the P-value? Use α = 0.01
What is the 99% confidence interval?
Table 2:
|
T\D |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
|
9 |
81 |
82 |
80 |
74 |
75 |
81 |
83 |
86 |
88 |
82 |
|
1 |
73 |
77 |
83 |
81 |
76 |
76 |
82 |
83 |
79 |
84 |
|
5 |
85 |
78 |
76 |
81 |
82 |
83 |
76 |
82 |
86 |
79 |
|
T\D |
11 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
19 |
20 |
|
9 |
80 |
78 |
84 |
75 |
84 |
78 |
77 |
79 |
84 |
84 |
|
1 |
80 |
84 |
82 |
83 |
75 |
81 |
78 |
85 |
85 |
80 |
|
5 |
76 |
76 |
78 |
72 |
84 |
76 |
74 |
85 |
82 |
79 |
|
T\D |
21 |
22 |
23 |
24 |
25 |
26 |
27 |
28 |
29 |
30 |
|
9 |
84 |
83 |
79 |
86 |
85 |
82 |
76 |
85 |
84 |
80 |
|
1 |
81 |
78 |
83 |
80 |
81 |
83 |
83 |
82 |
83 |
80 |
|
5 |
81 |
80 |
83 |
79 |
78 |
84 |
79 |
77 |
82 |
83 |
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