A design engineer wants to construct a sample mean chart for controlling the ser
ID: 329620 • 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 760 hours and a standard deviation of 41.5 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 3? (Keep one decimal place)
Sample Hours 1 723 747 765 748 2 766 787 766 746 3 745 786 761 752Explanation / Answer
Distribution is Normal.
Population Mean = 760hrs, Std. Dev = 41.5hrs
Sample mean is average of samples which is equal to 757.67hrs
But sample mean average life for sample 3 is equal to 761hrs
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