Perform Quality control

December 6, 2009
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Quality control measures are to be carried out throughout the project. As you carry out these planned measures/measurements/inspections you need to record the outcomes. The activities under the quality control head helps you asses the performance and recommend necessary changes, if any. Like any other process you take a set of inputs, process them using suitable and recommended tools & techniques and then the output documentation reflects the state of quality achieved as well as any process changes that are considered essential.

The Inputs

Quality control processes are based of statistical theories thus the team assigned to work on quality control will need to have a good grasp of applicable theories. Theories related to statistical controls as they apply towards sampling and probability is the vital areas where adequate familiarity is needed. Usually such a group, typically, is named a QC department or something similar. Their job is to carry out the planned QC processes and identify any shortcomings in product or process quality.

There are some terms that are often confused by many people including QC personnel. So they’ll need to be very clear about the distinctions in the terms discussed here. Prevention and inspection is a pair of terms which can be conflicting in their implications. While prevention looks at ways to keep errors out of a process, inspection is the act of keeping errors away from customer deliveries. Thus the context is different though the main purpose is to prevent errors in the product/process/project delivered to the end customer. Both are part of the QC process. Similarly the distinction between attribute sampling and variables sampling need to be understood well. Attribute sampling is a kind of discrete sampling process. Results either meet or fail to meet the success criteria. Variable sampling, on the other hand, checks items on a continuous scale to decide degree of conformance. Another such pair of terms whose implications should be clear are tolerance and control limits. Tolerance represents variations that are inherent. The variation in the output item caused even when a process is completely under control and thus acceptable. The variation threshold that determines the threshold that lets you conclude the process is out of control.

The inputs that you would use for the QC process would include (but not limited to), Project management plan as the overall reference for everything. Quality metrics and checklists will let you check for no-conformance easily. Work performance measurements tell you if the project process is working well. Change requests are generated when any deviations are noticed in quality or process improvement opportunities are found. These approved changes form inputs that add value to the QC process. You are able to judge the overall process better by taking the original baseline and the intended changes together for a bigger picture. Deliverable is the target we are chasing through executing the project. There is always learning involved through all this and you need to capture that in updating the organizational process assets.

Tools & Techniques that You Need to Use

Tools & techniques used are based on statistical and probability theory and some graphic techniques. In totality they form a body of knowledge that has come to be known as quality theory. The tools and techniques include and control charts, Pareto charts, histograms, cause & effect diagrams, run charts, flowcharts and scatter diagrams are various graphic techniques that are based on statistics and mathematics. Flow chart being a graphic tool that makes for easier understanding of a process. Statistical sampling and inspections are tools that help make drawing conclusions about quality achievements easier. Approved change requests are reviewed to make sure there are no superfluous changes and also that nothing significant has been missed.

One of the major responsibilities of QC activities is to determine the root cause of problems seen and thereby decide remedial actions that show up as process change request. The graphic tools from the above list that help do this analysis are the cause & effect diagrams, histogram and the Pareto chart, the run chart, the scatter diagram et al. The control chart helps determine when and where the process is likely to break. Pareto chart is a great tool for focusing on the primary causes for problems. Most of these techniques are also helpful in QA processes and have been discussed in some detail in an article about the tools and techniques for the QA process. Also review the discussions on the tools & techniques as appropriate for the QC processes are discussed in later articles.

Quality control measurements are recorded. These records sort of traces what has been happening about quality achievements over time. Validated changes form inputs to necessary improvements. These may be about confirming if the changes requested have been implemented appropriately. Validated deliverables identify if the deliverables are appropriates as per verify scope and forms the basis for customer acceptance. Process asset updates adds the necessary improvements to the asset documents- Completed checklists and lessons learned are the important ones.

Change requests take care of the necessary preventive/corrective actions for the process and they need to be incorporated into the process. Change management process should control the implementation of changes. Quality standards and any other project documents that need update should be changed after the QC activities at a specific time point is done.

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