Variability, which is also present in many processes, can be contained and managed too (for example see 6-Sigma, Statistical Process Control). For example, variability is found in the creation or execution of the following:

1. Product Requirements Specifications
2. Product development project processes
3. Production processes
4. Service & support processes
5. Delivery processes
6. Adherence of project and Product Requirements Specifications to market and user changes
7. Consistency of the development project
8. Consistency of Production Process
9. Continuous improvement
10. Verification of the design
11. Validation of the product

The basic methodology to solve the Quality implementation problem is to find the critical subset of variables used in the design of the product and processes: i.e.

• Determine product and process qualities that will meet or exceed user, market, and manufacturing needs and demands.
• Prioritize the criticality of the qualities and what needs to be controlled.
• Establish a measurable or assessable specification with tolerance(s) for each of the qualities.
• Produce control plans: e.g. means of measurement and control and acceptable variations allowed in the tolerances.
• Determine how to correct and eliminate or minimize the variations.

During this process always remember economic and technical reality: a push to "delight" the customer, over-design and over-specifying may cost time and money. This determination is where experience can be a significant and positive contributory factor.

Since some products will have many qualities to consider and measure, it may be easier to use sets of qualities in order to reduce complexity. A set of qualities is any set of similar measurable or objectively assessable qualities of a product (or a service or process).

Some examples of sets of qualities are:

• Electrical = {voltage, current, frequency, watts consumed/produced, EMI...}
• Software = {domains of program variables, ranges of program variables, algorithm speed, I/O speed, storage access time...}
• Cosmetic = {scratches, blemishes, knit marks, relief marks...}
• Manufacturing = {ambient particulate matter, speed of pick & place machine, size of drilled holes...}
• Product features = {number of interactive buttons, color of LEDs, timeliness of response to user inputs, recyclability...}
• Environmental = {EMC, altitude, external power, vibrations, hazardous substances, particulate contaminants...}