A quality analyst wants to construct a control chart for determining whether three machines, all producing the same product, are under control with regard to a particular quality variable. Accordingly, he sampled four units of output from each machine, with the following results: $$\begin{array} {r }
{ \text { Measurements } } \
\begin{array} { l l l l l }
\text { Machine } & \
\hline \# 1 & 17 & 15 & 15 & 17 \
\# 2 & 16 & 25 & 18 & 25 \
\# 3 & 23 & 24 & 23 & 22
\end{array}\end{array}$$ What are the x-bar chart three-sigma upper and lower control limits?
A) 22 and 18
B) 23.29 and 16.71
C) 23.5 and 16.5
D) 23.16 and 16.84
E) 24 and 16

Question

A quality analyst wants to construct a control chart for determining whether three machines, all producing the same product, are under control with regard to a particular quality variable. Accordingly, he sampled four units of output from each machine, with the following results: $$\begin{array} {r } 
{ \text { Measurements } } \
\begin{array} { l l l l l } 
\text { Machine } &   \
\hline   \# 1 & 17 & 15 & 15 & 17 \
\# 2 & 16 & 25 & 18 & 25 \
\# 3 & 23 & 24 & 23 & 22
\end{array}\end{array}$$ What are the x-bar chart three-sigma upper and lower control limits?
A) 22 and 18
B) 23.29 and 16.71
C) 23.5 and 16.5
D) 23.16 and 16.84
E) 24 and 16

Quizplus · Accepted Answer

The x-bar chart control limits are calculated using the average of the sample means and the standard deviation. The correct limits are 23.16 and 16.84.

A Quality Analyst Wants to Construct a Control Chart for Determining