Economic Design of and<i>R</i>Charts Under Weibull Shock Models
Bibliographic record
Abstract
This article considers the problem of a continuous production process, whose mean and variance are simultaneously monitored by and R control charts, respectively. The product variable quality characteristic is assumed to be normally distributed and the process is subject to two independent assignable causes (such as, tool wear-out, overheating, or vibration). One changes the process mean and the other the process variance. The occurrence of one kind of the assignable causes does not preclude the occurrence of the other kind. The occurrence times of the assignable causes are described by Weibull distributions having increasing failure rates. A cost model is developed for determining the economic design parameters. A non uniform decreasing sampling interval scheme is adopted to incorporate the effects of process deterioration. A two-step search procedure is employed to determine the economically optimum design parameters. The relative contribution of this article over the results obtained in Costa (1993 Costa , A. F. B. ( 1993 ). Joint economic design of and R control charts for process subject to two independent assignable causes . IIE Trans. 25 : 27 – 33 .[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) is addressed. This article introduces a few new assumptions and provides some theoretical derivations and results. These results may serve as readily available references for future studies. The article shows through numerical examples that ignoring the true (by assumption) Weibull shock model and incorrectly assuming exponential distributions of times to occurrences of assignable causes (and using constant sampling schemes), results in sizeable cost penalties. A sensitivity analysis of the model with respect to Weibull distribution parameters is performed.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.006 | 0.010 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".