Assignment 2: Controls As a quality analyst you are also responsible for controlling the weight of a box of cereal. The Operations Manager asks you to identify the ways in which statistical quality control methods can be applied to the weights of the boxe
Unit 4: Module 4 - M4 Assignment 2
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Assignment 2: Controls As a quality analyst you are also responsible for controlling the weight of a box of cereal. The Operations Manager asks you to identify the ways in which statistical quality control methods can be applied to the weights of the boxes. Provide your recommendations to the Operations Manager in a two-three page report. Using the data provided in the Doc Sharing area labeled M4A2Data, create Xbar and R charts. Your report should indicate the following along with valid justifications of your answers: a. The control limits of the weights of the boxes. b. Nonrandom patterns or trends, if any. c. If the process is in control. d. The appropriate action if the process is not in control..
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1. Find the mean of each subgroup Xbar(1), Xbar(2), Xbar(3)... Xbar(k) and the grand mean of all subgroups using:
2. Find the UCL and LCL using the following equations:
A(3) can be found in the following table: n A(3) n A(3) 2 2.659 6 1.287 3 1.954 7 1.182 4 1.628 8 1.099 5 1.427 9 1.032
3. Plot the LCL, UCL, centerline, and subgroup means
4. Interpret the data using the following guidelines to determine if the process is in control:
· One point outside the 3 sigma control limits
· Eight successive points on the same side of the centerline
· Six successive points that increase or decrease
· Two out of three points that are on the same side of the centerline, both at a distance exceeding 2 sigmas from the centerline
· Four out of five points that are on the same side of the centerline, four at a distance exceeding 1 sigma from the centerline f. Using an average run length (ARL) for determining process anomalies
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Example: The following data consists of 20 sets of three measurements of the diameter of an engine shaft. |
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n |
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#1 |
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#2 |
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#3 |
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StdDev |
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Xbar |
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1 |
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2.0000 |
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1.9998 |
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2.0002 |
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0.0002 |
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2.0000 |
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2 |
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1.9998 |
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2.0003 |
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2.0002 |
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0.0003 |
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2.0001 |
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3 |
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1.9998 |
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2.0001 |
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2.0005 |
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0.0004 |
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2.0001 |
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4 |
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1.9997 |
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2.0000 |
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2.0004 |
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0.0004 |
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2.0000 |
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5 |
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2.0003 |
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2.0003 |
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2.0002 |
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0.0001 |
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2.0003 |
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6 |
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2.0004 |
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2.0003 |
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2.0000 |
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0.0002 |
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2.0002 |
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7 |
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1.9998 |
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1.9998 |
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1.9998 |
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0.0000 |
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1.9998 |
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8 |
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2.0000 |
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2.0001 |
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2.0001 |
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0.0001 |
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2.0001 |
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9 |
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2.0005 |
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2.0000 |
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1.9999 |
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0.0003 |
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2.0001 |
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10 |
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1.9995 |
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1.9998 |
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2.0001 |
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0.0003 |
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1.9998 |
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11 |
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2.0002 |
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1.9999 |
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2.0001 |
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0.0002 |
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2.0001 |
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12 |
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2.0002 |
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1.9998 |
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2.0005 |
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0.0004 |
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2.0002 |
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13 |
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2.0000 |
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2.0001 |
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1.9998 |
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0.0002 |
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2.0000 |
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14 |
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2.0000 |
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2.0002 |
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2.0004 |
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0.0002 |
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2.0002 |
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15 |
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1.9994 |
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2.0001 |
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1.9996 |
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0.0004 |
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1.9997 |
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16 |
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1.9999 |
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2.0003 |
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1.9993 |
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0.0005 |
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1.9998 |
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17 |
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2.0002 |
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1.9998 |
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2.0004 |
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0.0003 |
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2.0001 |
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18 |
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2.0000 |
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2.0001 |
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2.0001 |
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0.0001 |
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2.0001 |
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19 |
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1.9997 |
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1.9994 |
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1.9998 |
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0.0002 |
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1.9996 |
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20 |
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2.0003 |
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2.0007 |
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1.9999 |
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0.0004 |
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2.0003 |
Sbar chart limits: SBAR = 0.0002
UCL = B(4) x SBAR = 2.568 x .0002 = 0.0005136 LCL = B(3) x SBAR = 0 x .0002 = 0.00
Xbar chart limits: XDBLBAR = 2.0000
UCL = XDBLBAR + A(3) x SBAR = 2.000+1.954 x .0002 = 2.0003908 LCL = XDBLBAR - A(3) x SBAR = 2.000-1.954 x 0002 = 1.9996092
S-Chart:
Xbar Chart:
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Note: The following consists of 12 sets of three box weights in ounces |
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N |
#1 |
#2 |
#3 |
StdDev |
Xbar |
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1 |
6.3 |
6.28 |
6.26 |
0.02 |
6.28 |
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2 |
6.32 |
6.32 |
6.33 |
0.005773503 |
6.32333333 |
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3 |
6.29 |
6.33 |
6.36 |
0.035118846 |
6.32666667 |
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4 |
6.3 |
6.29 |
6.34 |
0.026457513 |
6.31 |
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5 |
6.295 |
6.315 |
6.39 |
0.050083264 |
6.33333333 |
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6 |
6.292 |
6.319 |
6.33 |
0.019553346 |
6.31366667 |
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7 |
6.289 |
6.323 |
6.4 |
0.0568712 |
6.33733333 |
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8 |
6.286 |
6.327 |
6.471 |
0.097161378 |
6.36133333 |
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9 |
6.283 |
6.331 |
6.498 |
0.112855365 |
6.37066667 |
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10 |
6.28 |
6.335 |
6.525 |
0.128549601 |
6.38 |
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11 |
6.277 |
6.339 |
6.39 |
0.056589163 |
6.33533333 |
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12 |
6.274 |
6.343 |
6.4 |
0.063095166 |
6.339 |
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