Category Archives: Statistics

Statistical Methods/Control Charts

Question: My question is regarding a threading process.  There is 100% inspection for go/no go check and about 5% rejection/rework.  The batch size is 5,000 nos and is completed in 3 days of production. Two such batches are produced in … Continue reading

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Control Chart to Analyze Customer Satisfaction Data

Q: Let’s assume we have a process that is under control and we want to monitor a number of key quality characteristics expressed through small subjective scales, such as: excellent, very good, good, acceptable, poor and awful. This kind of data is … Continue reading

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AQL for Electricity Meter Testing

Q: We have implemented a program to test electricity meters that are already in use. This would target approximately 28,000 electricity meters that have been in operation for more than 15 years. Under this program, we plan to test a … Continue reading

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Variation in Continuous and Discrete Measurements

Q: I would appreciate some advice on how I can fairly assess process variation for metrics derived from “discrete” variables over time. For example, I am looking at “unit iron/unit air” rates for a foundry cupola melt furnace in which … Continue reading

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Could Null Hypothesis State Difference?

Q: Does a null hypothesis always state that there is no difference?  Could there be a null hypothesis that claims there is?  In the U.S. legal system, the null hypothesis is that the accused is assumed innocent until proven guilty.  In another legal … Continue reading

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