A design engineer want to construct a sample mean chart for controlling the service life of one of the types of light bulbs her company produces. She knows from numerous previous observations over many years that the output of the process is normally distribute with a mean service life of 700 hours and a standard deviation of 30 hours. On four recent production batches, she tested service life on random samples of ten bulbs.

(round all answers to 2 decimals)

1) What is the mean sample means (Grand means)?

2) What is the standard deviation of the distribution of sample mean?

3) What is the lower control limit (LCL) of the control chart (Z = 3)?

4) What is the upper control limit (UCL) of the control chart (Z = 3)?