Light bulbs are tested for their luminance, with the intensity of brightness desired to be within a certain range. Random samples of five bulbs are chosen from the output, and the luminance is measured. The sample mean and the standard deviation s are found. After 30 samples, the following summary information is obtained:

The specifications are 90 ± 15 lumens.
(a) Find the control limits for the - and s-charts.
(b) Assuming that the process is in control, estimate the process mean and process standard deviation.
(c) Comment on the ability of the process to meet specifications. What proportion of the output is nonconforming?
(d) If the process mean is moved to 90 lumens, what proportion of output will be nonconforming? What suggestions would you make to improve the performance of the process?

Transcribed Image Text:

5-2550 42195 Σ ー Σ.- = 2550 に1