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

Question

Quizplus · Accepted Answer

To find the standard deviation of the sample, we need to calculate the variance first.
Variance = (sum of squared deviations from the mean) / (sample size - 1)
The deviations from the mean are:
-32.6, 14.4, 3.4, 28.4, -146.6, 44.4, 28.4, 21.4, -25.6
Squared deviations are:
1062.76, 207.36, 11.56, 806.56, 21556.56, 1971.36, 806.56, 459.36, 656.36
The sum of squared deviations is 28438.76
The variance is 28438.76 / 8 = 3554.845
The standard deviation is the square root of the variance, which is approximately 58.5. Therefore, choice C is correct.

Quality Control Is an Important Issue at ACME Company Which