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

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 R chart is to be constructed for the number of blemishes. One way
to create the upper control limit involves multiplying the mean of the sample ranges by D4. For
this data set, the value of D4 is ________.