4-6 Quality control is an important issue at ACME Company which manufactures lig

Question

4-6 Quality control is an important issue at ACME Company which manufactures light bulbs. In order to conduct testing of the life hours of their light bulbs, they randomly sampled nine light bulbs and measured how many hours they lasted (mean = 346.6).
378, 361, 350, 375, 200, 391, 375, 368, 321

4. What is the range?
A. 342.43
B. 3424.3
C. 58.5
D. 191
E. 1060

5. What is the variance?
A. 342.43
B. 3424.3
C. 58.5
D. 191
E. 10609

6. What is the standard deviation?
A. 342.43
B. 3424.3
C. 58.5
D. 191
E. 10609

Explanation / Answer

378, 361, 350, 375, 200, 391, 375, 368, 321

4. Maximum value is 391.

Minimum value is 200.

Range = Maximum value - Minimum value

= 391 - 200

= 191.

5. Given mean = 346.6

Variance = (((378 - 346.6)2 + (361 - 346.6)2 + (350 - 346.6)2 + (375 - 346.6)2 + (200 - 346.6)2 + (391 - 346.6)2 + (375 - 346.6)2 + (368 - 346.6)2 + (321 - 346.6)2 +) - 346.62) / 8 = 3424.38

= B.3424.3.

6. Standard deviation = 3424.3 = 58.5167

= C. 58.5

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