Question

QUESTION 12 A design engineer wants to construct a sample mean chart for controlling the service life of a halogen headlamp his company produces. He knows from numerous previous samples that this service life is normally distributed with a mean of 500 hours and a standard deviation of 20 hours. On three recent production batches, he tested service life on random samples of four headlamps, with these results: Service life in hours Sample 1 Sample 2 Sample 3 Sample 4 Observation 1 495 500 505 500 Observation 2500 490 456 490 Observation 3505 456 485 474 Observation 4 500 490 474 504 What is the sample mean service life for sample 2? 460 hours 484 hours 492 hours 499 hours 502 hours

Answer 1

Answer 2= Sample mean of sample 2=(500+490+456+490)/4 =484 hours

So the correct answer is 484 hours

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