X Bar and R chart....Please help

#1
Components used in a digital SLR camera are manufactured with nominal dimension of 0.3 mm and lower and upper specification limits of 0.295 mm and 0.305 mm respectively. The x bar and R control charts for this process are based on supgroups of size 5 and they exhibit statistical control, with the center line on the x bar chart at 0.3020 mm and the center line on the R chart at 0.0014 mm.

a) estimate the mean and the standard deviation of this process?
b)Suppose that parts below the lower specification limits can be reworked, but parts above the upper specification limit must be scrapped. Estimate the proportion of scrap and rework produced by this process.
c)Suppose that the mean of this process can be reset by fairly simple adjustment. What value of the process mean would you recommend?
Estimate the proportion of scrap and rework produced by this process at this new mean.


Please help me :"( I don't get it.
 
#3
Thank you so much for you clarification . But the answer to part b gives me both zero??!! is it correct?
 
Last edited:

Miner

TS Contributor
#7
I did not calculate the z scores but the mean +/- 3s falls well within both specifications, so the answer to both should be zero.