Question

Please answer the following questions.

1- List at least three characteristics of data plotted on a p , np , c, or u control chart that would indicate that a process is stable

2- If a process cycle is 24 hours, Explain How often you should sample this process in order for your data to be representative of all potential sources of variation?

3- If your defective rate is 4%, what should your sample size be in order for your control chart boundaries to include enough data points for analysis

4- Can a stable process produce defective parts? If yes can you predict that?

Answer 1

1) List at least three characteristics of data plotted on a p , np , c, or u control chart that would indicate that a process is stable

Ans :-

p chart - A p-chart is an attributes control chart used with data collected in subgroups of varying sizes. Because the subgroups size can vary, it shows a proportion on non conforming items rather than the actual count. P-charts show how the process changes over time.

np- chart :- an np-chart is an attribute control chart used with data collected in sub group that are the same size. Np-chart shows how the process,measured by the number of non conforming item produced change over time. The process arrtibute is always described in yes /no, pass/fail go/no go from.

C-chart :- a c-chart is an attributes control chart used with data collection in sub group that are the same size. C-chart shows how the process, measured by the number of non conformities per item or group of items, change over times. Non conformities are defects or occurrence found in the sampled sub group.

3) If your defective rate is 4%, what should your sample size be in order for your control chart boundaries to include enough data points for analysis.

Answers :-

Control boundaries is always 3 sigma of upper side from Mean (x bar ) and lower sides of 3 sigma from Mean (x bar) .

4) Can a stable process produce defective parts? If yes can you predict that?

Answers:-

Yes, Because stable process is one where the variation are predictable and cause of the the variation are also predictable and are common causes inherent within the system. Basically all possible special cause of variation in the system are understood and addressed. Capable or stable process is primarily stable and in addition it is good enough to meet the specification goals consistently.