Controlling Project Quality

Perform Quality Control

“If you don’t have time to do it right you must have time to do it over.”


The main goal of a project is to produce a product, service or result. Quality control project management activity is the one where the team verify whether the project is producing what it is intended to, adhering to the documented requirements.

Quality control is about testing the deliverables to find any defects. If and when a defect is found you find the root cause of it and,

(a) fix the defect (which may need you to raise a change request),

(b) ensure that the root cause is addressed so such defects will not occur in future.

This project management activity is all about using statistical tools. The following concepts are something that the quality control team should be aware of.

Prevention versus Inspection

Prevention is about taking proactive action to ensure defects are not introduced in the product. Creating check-lists, training people in testing methods, creating effective test plan – these are all preventive acts.

Inspection is about examining deliverables with intent to find any defects, or deviations from documented requirements, so that customer gets the deliverables that implement given requirements. Quality control activities are conducted from this perspective.

Preventive activities are done before producing deliverables, and Inspection activities after.

If you don’t have time to do it right you must have time to do it over.

— Unknown

Attribute Sampling versus Variables Sampling

First let us understand what is meant by ‘sampling’. Sampling is a statistical technique of assuring quality where a subset of large population is selected and certain characteristics are closely examined on that subset. If the characteristics meet specified standards then entire population is certified to be good, else entire population is rejected. Advantage of Sampling approach is that it reduces quality testing time and lowers quality assurance cost.

Now, Attribute sampling is the case of sampling where population is accepted if characteristics met specifications exactly; if they didn’t the population got rejected.

Variables sampling is the case where the degree to which characteristics matched specifications is measured. The population is accepted only if they matched to a certain degree of conformity. In other words, tolerance is introduced. In Attribute sampling tolerance is zero – characteristics either matched, or they did not.

Tolerances versus Control Limits

We saw the introduction of tolerance in previous paragraph. Tolerance indicates a range of deviation within which the results are accepted. Control limits are the thresholds of deviation beyond which the process is termed as ‘out of control’.

What do I need to test project deliverables?

Project management plan

By now you might have come to expect what goes in from project management plan for this process. Yes, the Quality management plan.

Quality management plan refers to organization’s policies related to quality, and contains the following information –

  • how quality is measured on the project
  • what quality control and assurance activities are conducted, their frequency and duration
  • acceptable quality standards

Project Quality Metrics

A project quality metric refers to its attribute that is to be measured, and also how it is to be measured. A quality metric measurement is the actual value of this metric.

For instance, tire-alignment is an attribute of the car and a quality metric for it defines how to measure tire alignment, including tolerance limits. Metrics help you verify quality against requirements.

Project Quality Checklists

A checklist continuously gets refined as project progresses. A good quality checklist will help to verify quality of the product to a large extent. It is a structured list of predefined checks that help you to confirm that deliverables meet requirements. Certain industries have standard checklists.

Deliverables and Approved change requests

Two things that need to be verified on a project are – deliverables and change requests. Deliverables are what the project produces. QC (quality control) team needs to check quality of deliverables against documented requirements.

Certain change requests are part of the deliverables based on their status in change control list. Whichever have been approved by the change control board and planned to be delivered, need to be verified by the QC team in this process.

Every organization has some quality guidelines, policies, standards, issues and defect reporting methods that need to be considered for the process.

How do I do it?

Seven basic quality tools 

We have seen this in the post describing how Quality is planned. While you can revisit that lesson for more details, the list of these 7 tools are –

  1. Cause-and-effect diagrams
  2. Flowcharts
  3. Checksheets
  4. Pareto diagrams
  5. Histogram
  6. Control charts
  7. Scatter diagram

Statistical sampling

Statistical sampling is a sampling technique where a representational sample is picked from the population and this sample is thoroughly tested using the designed tests. If number of defects found cross the acceptable limit in this sample, entire population is rejected.

For instance, out of 10000 shirts (population) a lot of 100 shirts is randomly selected. Each of these shirts are tested for manufacturing defects. If the threshold is say 3 shirts, then 3 defective shirts at the most are allowed in this lot of 50 shirts. If more than 3 defective shirts are found, then entire population of 10000 shirts are rejected.

statistical samplingFigure 1: Statistical sampling flow


Inspection is a non-intrusive way of verifying quality of a finished product by formal evaluation exercise against documented standards. This is mostly a manual exercise. Specific attributes to test and the method of inspection are understood from the Quality management plan.

Inspection is used to validate deliverables as well as defect repairs, which might come as a result of implementing change requests.

Review of approved change requests

Just as deliverables, approved change requests too are verified for intended quality as per the guidelines from Quality management plan.

What do I produce in this activity?

Measured values of Quality metrics

All QC measurements are documented in the format specified in Quality management plan. These form inputs to Perform Quality Assurance process.

Validated changes & Verified project deliverables

Deliverables and changes both go through quality control process and rejected changes will go back to execution phase.

Change requests

As with any monitor and control process, changes may be discovered during this process to, say, project management plan itself. In such cases a change request is raised that goes through change control board via Perform Integrated Change Control process

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