Process
Control: Authentic Learning Task 2 - Hats Off to Us!
Background
The p chart is used to control the
proportion of nonconforming (discrepant or defective) items found
in a sample (group) being inspected. This could be a group of
50 parts that are 100% functionally tested or the proportion of
on-time deliveries etc.
For example, at a final inspection station a 100% visual inspection could be performed on a refrigerator for several characteristics such as paint runs, dirt in the paint, door fit (go-nogo gage), required informational stickers, etc. The inspector would check for each of the possible problems and if at least one discrepancy was found then the refrigerator would be considerred nonconforming. At the end of the shift the fraction nonconforming would be calculated and ( i.e. 17 nonconforming out of 340 refrigerators or 0.05 or 5% nonconforming) plotted on a p chart.
A p chart would display the fraction nonconforming shift by shift for a two week time span.
Web sites
isixsigma - http://www.isixsigma.com/offsite.asp?A=Fr&Url=http://www.sytsma.com/tqmtools/charts.html
Health tactics example - http://www.healthtactics.com/link4p.htm
Statlets background for their software and example - http://www.statlets.com
Another Health care example - http://www.robertluttman.com/vms/Week5/page5.htm
Statsoft- http://www.statsoft.com/textbook/stquacon.html#variables
Read Authentic Learning Task #2 Hats off to Us! in the Process Control Participant Guide pages 33- 38.