A design engineer wants to construct a sample mean chart for controlling the ser

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? (Keep two decimal places)

Your Answer:

Explanation / Answer

Considering the given question and the details of hours of service life for Sample-2 are as follows,

Mean can be defined as the average of all the entities considered for calculation

Hence in this case,

Mean = (Sum of total of all hours for sample-2) / Count of number of individual entities considered

Therefore,

Mean = (x1 + x2 + x3 + x4) / 4

(Since total no of entries in sample-2 is only 4)

Mean = (511+506+498+476) / 4

= 1991 / 4

Mean = 497.75

Hence for Sample-2, Mean is 497.75.

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