Question

need answer to these true-false questions.

1-) When the sample size n is moderately large, say n > 10 or 12, x̅ and R charts are preferable to X̅ and s charts.

2-) If Cp >1, the process uses up more than 100% of the specification band

3-) An assumption in the performance properties of x̅ and R control charts is that the underlying distribution of the quality characteristic is normal.

4-) Average time to signal is the expected number of samples taken before the shift is detected.

5-) x-charts monitor within-sample variability

Answer 1

1. True

As R chart tells you about the short time variation and used for very small n and it depends on ranges for estimating the stndard deviation But S chart depends on the sample standard devaiation for estimation of standard deviation so fo n of samoke size 10 to 12 it is recommended X bar s chart than X bar r chart

2. False if Cp the process capability is less than one then the process variation uses more than 100% of the specification band

3. True Quality charecteristics is to be modeled to normal distribution in Xbar and R chart

4. False It is not ATS Average time to signal but ARL averge Run Length which is taken before the shift is detected

5. False - it is between variability not within