Fifteen subgroups of five parts each are collected (five consecutive parts every hour for 15 hours). a critical to quality dimension is measured and the average and range are calculated for each of the fifteen subgroups. the grand average (average of the 15 averages) is calculated to be 18.37 mm and the average range (average of the 15 ranges) is calculated to be 0.113 mm. what is the lower control limit on the average chart?

(co 3) the times that customers spend in a book store are normally distributed with a mean of 39.5 minutes and a standard deviation of 9.4 minutes. a random sample of 25 customers has a mean of 36.1 minutes or less. would this outcome be considered unusual, so that the store should reconsider its displays? no, the probability of this outcome at 0.035, would be considered usual, so there is no problem yes, the probability of this outcome at 0.035, would be considered unusual, so the display should be redone no the probability of this outcome at 0.359 would be considered usual, so there is no problem yes, the probability of this outcome at 0.965 would be considered unusual, so the display should be redone