Question 3 a Explain why it is important to consider variati

Question 3)

a. Explain why it is important to consider variation about the nominal as a measure of product/process performance; that is, why it is not sufficent or advisable to consider only peformance on average ?

b) What is meant by the statement that a process is in a state of statistical control

c) If a process is in a state of statistical control, does it necessarily follow that all or nearly all of the units of the product produced will be within the specification limits ?

Solution

a) average never gives the better idea , beacause there might be some experimental values which are acting as anomalies in the production process, therefore it is necessary to count variation about nominal as the method to access product performance. Also it gives a limit upto which we can accept the quality of the product.

b) SPC statistical process control is a method in which statistics is used to monitor and control a method. Main aim is to control process so that is operates at full potential as well as the waste produced is reduced.SPC can be applied to any process where the \"conforming product\" (product meeting specifications) output can be measured. Key tools used in SPC includecontrol charts; a focus on continuous improvement; and the design of experiments. An example of a process where SPC is applied is manufacturing lines

c) No it does not imply that all the units are in a specified limit . but majorly production lies in a 95% confidence interval with very less variation , either positive or negative. For example in packing of a cereal some packaging may have high weight some may have less. So it also depends on the significance level which is choosen to limit the variation interval.