A design engineer wants to construct a sample mean chart for controlling the ser
ID: 381838 • Letter: A
Question
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:
What is the sample mean service life for sample 2?
Sample Hours 1 503 501 491 491 2 499 501 500 512 3 509 505 515 507Explanation / Answer
Sample mean service life for sample 2 = average hours of four headlamps tested in sample 2
Sample mean service life for sample 2 = (499 + 501 + 500 + 512)/4 = 503
Sample mean service life for sample 2 is 503 hours
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