Perform Quality Assurance – III

December 5, 2009

Tools & techniques used in the perform quality control and the quality audit and the process analysis techniques will be discussed in this part 2 article.

Techniques in the perform QC

These include cause & effect diagrams, control charts, flowcharting, histogram, Pareto chart, run chart, scatter diagram, statistical sampling, inspections and approved change requests reviews. Of these the techniques of control charts, flowcharting, statistical sampling has been discussed in part 1 and elsewhere so they’ll not be discussed again here.

Cause & effect diagrams, fishbone diagrams or the ishikawa diagrams are different names attached to the technique. Different types of potential causes are drawn on a line progressing towards a cause, such as a major defect. The diagram looks like a fishbone, leading to its head, the major problem. Root causes are then discovered by following a set of questions why-why or how-how kind of reasoning and bringing out possible causes. The two diagrams indicated in the PMBOK (figs. 8-12 and 8-13) illustrate the way it is used.

The histogram technique is to create bar charts of frequency of occurrence of some attributes of a problem. The reasons will have different frequency of operation. The attribute that happens most frequently is the most common cause of the problem being studied.

In the Pareto charts the histogram is a ranked one with the higher bars coming first. A cumulative frequency distribution also is plotted. So that it is immediately evident which 20% of the causes create 80% of the problems (as stated by Pareto in his law). That illustrates very starkly the causes to focus on.

Run charts are the control charts without the control limits displayed. It is simply a record of how things are going; so that mathematical trend analysis etc can be carried out of the curve that shows up. The analysis looks at historical data and attempts to predict the future trend. Trend analysis can be used to monitor technical performance as well as cost and schedule performance. You could deduce how many errors/defects have been identified and how many of them remain to be corrected. For cost and schedule performance you could look at how many activities per period were completed with noticeable variations. One could see from the graph, qualitatively what kind of variations are happening, if deviations are increasing or decreasing etc.

Scatter diagrams let you confirm if correlation exists between two variables. When plotted against each other, if the diagram resembles values that are scattered all over the graph area, then they are not related. Whereas a diagram that is close to a diagonal indicates strong correlation between the two variables.

Inspection is a technique of taking measurements and determining if an item does conform to a specified quality level. Inspections could be carried out to determine root causes too.

Review of change requests ensures that the requests have been studied thoroughly and no superfluous changes are carried out. Quality audits are also reviews that are used heavily to do a structured and independent review. Audits help identify best practices being used, gaps/shortcomings, share best practices from elsewhere, help the team to achieve higher productivity as also improve the lessons learnt knowledgebase of the organization.

Lastly, process analysis is another important tool to help identify process improvement opportunities and if some non-value add step could be removed altogether. Process changes necessary to correct and prevent errors are also possible.

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