Question

A salon and spa chain periodically analyzes its service times to check for variation in service processes using x-bar and R charts. Daily random samples, each containing service times observed with eight different customers are collected. The average mean and the average range of the service times for the past week were 27.2 and 3.76 minutes, respectively. The value of D4 for a sample size of eight is 1.864. What is the upper control limit (UCL) for the R-chart

Answer 1

7.00864

Explanation:

The upper control limit for R -chart can be computed by using following formula

UCL=Rbar*D4.

We are given that average range R bar is

Rbar=3.76.

The value of D4 for n=8 is also given that is

D4=1.864.

Thus, the required computed upper control limit is

UCL=3.76*1.864=7.00864.