Question

A junior engineer has to build a sample mean chart for the machines making Oreo cookies. He knows from numerous previous samples that this service life of the cream injectors is normally distributed with a mean of 760 hours and a standard deviation of 41.5 hours.

In the last three weeks, he tested the service life on random samples of four production runs with these results:

Sample	Hours
1	721	765	762	784
2	784	782	764	747
3	764	787	756	776

What is the value of x double bar? (Keep one decimal place)

Answer 1

B6 xAVERAGE(F2:F4) 1 Sample 721 784 764 Hours 765 782 787 762 764 756 784 747 776 X bar (mean of sample) 758 769.25 770.75 4 6 X double bar 766.0

1 Sample Hours X bar (mean of sample) 721 784 764 765 762 784 FAVERAGE(B2:E2) 782 764 747 FAVERAGE(B3:E3) 787 756 776 FAVERAGE(B4:E4) 6 X double bar FAVERAGE(F2:F4)