In order to determine if the time required for students to take a final exam is excessive,five students were selected at random from each of six classes.If the process average is 123.77 minutes and the average range is 66.83 minutes,the upper and lower control limits of a 3-sigma R-chart are
A)UCL = 141,LCL = 0
B)UCL = 133.6,LCL = 0
C)UCL = 96,LCL = 0
D)UCL = 152.3,LCL = 0

Question

Quizplus · Accepted Answer

The upper control limit (UCL) of a 3-sigma R-chart is calculated as UCL = D4 * R, where D4 is a constant that depends on the sample size and R is the average range. For a sample size of 5, D4 = 2.114. Therefore, UCL = 2.114 * 66.83 = 141. The lower control limit (LCL) of a 3-sigma R-chart is always 0.

In Order to Determine If the Time Required for Students