Instruction 18-7
a Factory Supervisor Is Concerned That the Time

Multiple Choice

Instruction 18-7
A factory supervisor is concerned that the time it takes workers to complete an important production task (measured in seconds) is too erratic and adversely affects expected profits. The supervisor proceeds by randomly sampling five individuals per hour for a period of 10 hours. The sample mean and range for each hour are listed below.
She also decides that lower and upper specification limit for the critical-to-quality variable should be 10 and 30 seconds, respectively.
$$\begin{array} { | l | l | l | } \hline \text { Hour } & \underline { \underline { X } } & \underline { R } \\\hline 1 & 18.4 & 25 \\\hline 2 & 16.9 & 27 \\\hline 3 & 23.0 & 30 \\\hline 4 & 21.2 & 23 \\\hline 5 & 21.0 & 24 \\\hline 6 & 24.0 & 25 \\\hline 7 & 19.3 & 12 \\\hline 8 & 15.8 & 14 \\\hline 9 & 20.0 & 13 \\\hline 10 & 23.0 & 11 \\\hline\end{array}$$
-Referring to Instruction 18-7,suppose the sample mean and range data were based on six observations per hour instead of five.How would this change affect the lower and upper control limits of an R chart?

A) Both LCL and UCL would remain the same.
B) LCL would remain the same; UCL would decrease.
C) LCL would increase; UCL would decrease.
D) LCL would decrease; UCL would increase.