A design engineer wants to construct a sample mean chart for controlling the ser
ID: 331115 • 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 1 764 771 754 760 2 776 787 768 747 3 779 759 783 753Explanation / Answer
The question clearly states that the population Mean is 760 hours and the standard deviation is 41.5 hrs.
Thre are 3 samples taken from the population 1, 2 and 3.
The samples have been tested 4 times and the mean of sample 3 is
mean of service life 3= (Sum of all 4 tests of sample 3)/4
mean of service life 3 = (779+759+783+753)/4
mean of service life 3= 768.5 hrs
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