SCENARIO 18-7
a Supplier of Silicone Sheets for Producers of Computer

Short Answer

SCENARIO 18-7
A supplier of silicone sheets for producers of computer chips wants to evaluate her manufacturing
process. She takes samples of size 5 from each day's output and counts the number of blemishes on
each silicone sheet. The results from 20 days of such evaluations are presented below. $$\begin{array}{l}\text {\quad\quad\quad\quad\quad\quad\quad Sheet }\\\begin{array} { r r r r r r r r } \underline {\text { Day } }& \underline { 1 } &\underline { 2 }&\underline { 3 }& \underline {4 }& \underline {5} & \underline { \text { Mean } } &\underline { \text { Range }} \\1 & 8 & 10 & 14 & 6 & 5 & 8.6 & 9 \\2 & 8 & 13 & 6 & 6 & 10 & 8.6 & 7 \\3 & 10 & 12 & 7 & 7 & 9 & 9.0 & 5 \\4 & 5 & 9 & 12 & 7 & 10 & 8.6 & 7 \\5 & 8 & 3 & 8 & 9 & 10 & 7.6 & 7 \\6 & 9 & 7 & 9 & 6 & 9 & 8.0 & 3 \\7 & 10 & 10 & 5 & 7 & 6 & 7.6 & 5 \\8 & 10 & 9 & 10 & 6 & 5 & 8.0 & 5 \\9 & 6 & 10 & 6 & 9 & 9 & 8.0 & 4 \\10 & 6 & 9 & 8 & 6 & 8 & 7.4 & 3 \\11 & 8 & 5 & 6 & 10 & 10 & 7.8 & 5 \\12 & 6 & 4 & 7 & 7 & 12 & 7.2 & 8 \\13 & 7 & 5 & 7 & 6 & 9 & 6.8 & 4 \\14 & 5 & 8 & 8 & 7 & 6 & 6.8 & 3 \\15 & 7 & 12 & 10 & 6 & 10 & 9.0 & 6 \\16 & 7 & 11 & 4 & 7 & 8 & 7.4 & 7 \\17 & 8 & 4 & 5 & 4 & 7 & 5.6 & 4 \\18 & 11 & 4 & 11 & 11 & 10 & 9.4 & 7 \\19 & 6 & 10 & 6 & 10 & 10 & 8.4 & 4 \\20 & 6 & 12 & 12 & 6 & 8 & 8.8 & 6\end{array}\end{array}$$ She also decides that the upper specification limit is 10 blemishes.
-Referring to Scenario 18-7, an $\bar { X }$ chart is to be used for the number of blemishes. One way to
obtain the control limits is to take the grand mean and add and subtract the product of A2 times
the mean of the sample ranges. For this data set, the value of A2 is ________.