A 10 random-sample evaluation of the specification 75 3 yielded readings of 77.1, 76.8, 76.3, 75.9, 76.1, 77.7, 76.7, 75.7, 76.9, 77.4.
(a) Determine the sample mean and the 95% confidence interval for the population mean.
(b) Determine the sample standard deviation and the 95% confidence interval for the population standard deviation.
(c) Display the data using a histogram and normal probability plots.
(d) Using plots and Z table estimate the proportion beyond the specification limits. Determine the process capability/performance indices. Comment on the validity of the analysis and results.
(e) Determine where emphasis should be given to make the process more capable of meeting specifications (reducing variability or shifting mean).
(f ) Give an example from manufacturing, development, and service where these data might have originated.