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:
Sample SERVICE LIFE

1 495 500 505 500

2 525 515 505 515

3 470 480 460 470

What is the sample mean service life for sample 2?

A) 460 hours

B) 495 hours

C) 515 hours

D) 525 hours

Answer 1

Answer:

C) 515 hours

Explanation:

The mean is the central value of set of numbers.

It is calculate by adding all the values together and then, divide by the quantity of items

 ∑ x

--------

  n

∑ =525 + 515 + 505 + 515 = 2,060

now we divide this value by the total number of items. Notice we take four headlamps so we divide by tis amount:

Mean = 2,060 / 4 = 515