Exam 19: Statistical Methods for Quality Control

A production process is considered in control if no more than to 6% of the items produced are defective. Samples of size 300 are used for the inspection process. a.Determine the standard error of the proportion. b.Determine the upper and the lower control limits for the P chart.

If the lower-control limit of a P chart is negative,

A production process is considered in control if it processes at least 98.5% non-defective items. Samples of size 400 are used for the inspection process. Determine the upper and lower control limits for the P chart of defective elements.

The results of inspection of samples of a product taken over the past 10 days are given below. Sample size for each day has been 140. Determine the 97% upper and lower control limits for the p-chart.

A production process that is in control has a mean (µ) of 200 and a standard deviation ( $\sigma$ ) of 22. Determine the lower and the upper control limits for sample sizes of 49.

The quality control department of a company has decided to select a sample of 20 items from each shipment of goods it receives and inspect them for defects. It has been decided that if the sample contains no defective parts, the entire lot will be accepted. a.What is the probability of accepting a lot that contains 10% defective items? b.What is the probability of accepting a lot that contains 5% defective items? c.What is the probability of rejecting a lot that contains 15% defective items?

Variations in process output that are due to factors such as machine tools wearing out are

Chocolate, Inc. manufactures 4 ounce chocolate bars. Random samples of size four were taken and weighed. Eight hours of observation provided the following data. a.Determine the 3 sigma upper and lower control limits for the x-bar chart. b.Determine the 3 sigma upper and lower control limits for the R-chart.

A production process is set up to fill containers with 16 ounces of liquid. The standard deviation $\sigma$ is known to be 0.5 ounces. The quality control department periodically selects samples of 25 containers and measures the contents. (Assume the distribution of filling volumes is normal.) a.Determine the upper and lower control limits. b.Explain the meaning of the values you found in part