My Reading on ASQ CQA HB Part V Part 2
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Charlie Ch<strong>on</strong>g/ Fi<strong>on</strong> Zhang<br />
<strong>Part</strong> VE<br />
Types Of Sampling<br />
Populati<strong>on</strong> sampling is the process of taking a subset of subjects that is representative of the entire populati<strong>on</strong>. The sample must<br />
have sufficient size to warrant statistical analysis.<br />
https://explorable.com/populati<strong>on</strong>-sampling<br />
• Haphazard sampling/ C<strong>on</strong>venient/ Accidental.<br />
Haphazard sampling is used by auditors to try to gather informati<strong>on</strong> from a representative sample of a<br />
populati<strong>on</strong>. Items are selected without intenti<strong>on</strong>al bias and with the goal of representing the populati<strong>on</strong> as a<br />
whole. The auditor might ask to see the deficiency reports <strong>on</strong> the coordinator’s desk. These reports might be<br />
rati<strong>on</strong>alized as being random and as representing the populati<strong>on</strong> as a whole. The auditor might ask for 10<br />
deficiency reports, two from each line, and will ask to be the <strong>on</strong>e who picks them. This might be rati<strong>on</strong>alized as<br />
removing the bias from having the coordinator select the sample.<br />
The pro side of haphazard sampling is that it is easy to select the sample, so the audit can be completed more<br />
quickly. There is less preparati<strong>on</strong> time, making it possible to do more audits.<br />
The c<strong>on</strong> side of haphazard sampling may outweigh its advantages. If the coordinator is reviewing the<br />
deficiency reports for a specific department at the time the auditor walks in, the results of the audit will show<br />
that this department has a disproporti<strong>on</strong>ate number of deficiencies when compared with the other departments<br />
in the sample. The auditor might pick deficiency reports that catch his or her eye for some unknown reas<strong>on</strong>,<br />
thus introducing an unknown bias. Haphazard sampling is the easy approach to sampling, but the results may<br />
not reflect all departments, lines, items, people, problems, or a myriad of other c<strong>on</strong>siderati<strong>on</strong>s. The results are<br />
not statistically valid, and generalizati<strong>on</strong>s about the total populati<strong>on</strong> should be made with extreme cauti<strong>on</strong>. The<br />
results of haphazard sampling are difficult to defend objectively.<br />
Of all the n<strong>on</strong>-statistical audit sampling methods, haphazard is arguably the worst.
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