Lec 13 - Individual Control Charts & EWMA

Lec 13 - Individual Control Charts & EWMA - Control...

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Unformatted text preview: Control Charts for Individual Measurements Sometimes repeated measures in a subsample don't make sense oven temperature inventory level accounts payable If variation in subsample only reflects measurement error, use individual measurements Process Industries Individual Control Charts 1. not for saving money on sampling 2. sample points must be relatively frequent 3. there is more sampling error (false alarm & insensitivity) 4. sample points tend to be non-normal (not averages, central limit thm does not apply) 2 Two Methods 1. X and Moving Range (R m ) Chart 2. **EWMA & X Chart 3 X and Moving Range (R m ) Charts X Chart: sample statistic: X Moving Range Chart: sample statistic: R 2 or R 3 Computation of the Moving Range X R 2 R 3 14.56 -- 13.88 0.68- 13.98 0.10 0.68 14.50 0.52 0.62 14.22 0.28 0.52 ... 4 Computing Control Limits 1. From initial data compute X and R m 2. Control Limits for R m chart UCL = D 4 R m CL = R m LCL = D 3 R m 3. Control Limits for X Chart = R...
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Lec 13 - Individual Control Charts & EWMA - Control...

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