Question 42

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 Hours 499 501 501 496 2 504 493 506 498 3 515 510 494 497 What is the sample mean service life for sample 27 (Keep two decimal places)