A bulb production line's voltages are monitored by control charts, with a Phase 1 control chart of sum sigma x_i = 361.5 & sum sigma R_i = 6.72, with n=4.

 

i) Bulbs with voltages less than LSL (lower specification limit) are scrapped & those with voltages above USL are reworked. If LSL= 11.8 & USL=12.2, how much is scrapped if the process small sigma (o) is cut by 25%?

 

ii) With unreduced variance, what's the PCR of the process?