Exam 17: Statistics for Quality: Control and Capability

The 68-95-99.7 rule tells us that if a process with mean  and standard deviation  varies according to a Normal distribution,then almost all measurements on individual products will lie in the range  ± 3.What do we call the values  - 3 and  + 3?

An important characteristic in the proper operation of ignition keys for automobiles is the groove width of the key.In a large manufacturing plant that produces thousands of keys,control charts have been established to monitor the process of cutting the groove.It is believed that the measurement (in inches)of the groove width is Normally distributed.Over a period of time,20 samples,each of size n = 5,were selected in order to establish 3-sigma and s charts.From these samples the following were determined: = 0.15932 and = 0.0193438.For the chart that is being set up,what are the appropriate 3-sigma lower and upper control limits, (LCL,UCL)?

What do we call the ability of a process to meet or exceed the requirements placed on it?

Piston rings for an automotive engine are produced by a forging process.We monitor the inside diameter of the rings manufactured by this process using an and an s control chart.Samples of size 4 are taken at regular intervals,and the sample means and standard deviations are computed and plotted on the charts in time order.The overall mean of the sample means is 73.812 millimeters,and the mean of the sample standard deviations is 0.022 millimeters.The control chart constants are (partially)reproduced below. What is the value of the upper control limit for the chart?

A p chart is a control chart based on plotting ____________.

When we examine and s charts,what is the best strategy to use?