4QA3 F12 Week 3 Lecture Notes

Gandomi 33 17 samples of 50 disks sample 1 2 3

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Unformatted text preview: inutes) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 7 6 UCL = 5.9 5 4 3 R = 2.6 2 Each data point on the top chart represents the average of a subgroup. Each corresponding point on the lower chart represents the range within that subgroup. 1 0 1 4QA3 F12 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 A. Gandomi 29 ●  A process is in control if: 1.  2.  Most points near process average, 3.  About equal number of points above and below centerline, 4.  4QA3 F12 No sample points outside limits, Points appear randomly distributed. A. Gandomi 30 ●  Based on in- control data ●  If non- random causes present discard data ●  Correct control chart limits ●  Sample size o  o  4QA3 F12 Attribute: more than 30 Variable: more than 4 A. Gandomi 31 ●  Take periodic samples from process ●  Plot sample points on control chart ●  Determine if process is within limits ●  Prevent quality problems 4QA3 F12 A. Gandomi 32 ●  ●  Subgroups for p charts are typically larger than for X bar and R charts. For most applications n>30 should suf3ice. The upper and lower control limits are given by: UCL = p + 3 LCL = p − 3 ●  p (1 − p ) n p (1 − p ) n where p bar is the average of the observed values. Use limits of +3/- 3 when unequal subgroup sizes and plot these values: Z= 4QA3 F12 p− p p (1 − p ) n A. Gandomi 33 17 samples of 50 disks SAMPLE 1 2 3 : : 17 4QA3 F12 NUMBER REJECTED 3 10 13 : : 7 117 A. Gandomi PROPORTION .06 .02 .26 : : .14 34 total rejected p = total sample observations = 117 / 17(50)...
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