Variation

Variation can be positive in contexts like "varied workday," "varied training", etc.

For manufacturing companies variation can create headaches and huge cost.

Variation of process parameters can cause the product quality to vary more than desired. 

All processes are subject to variation. Some might protest, but if you go into depth of things, you will always find differences. Two "identical" houses will be different if you study them more closely; nails are placed differently, the wood will be slightly different and have branches in different locations, etc. 

In the "old days", there were many creative explanations of natural variation; if one failed to churn butter, someone was in love. The norwegian fishermen have a funny explanation for poor fish catches; bad "Haill". You have to ask them what it means; I am not going to explain it here...

Some processes have little variation, while others have wide natural variation. For manufacturing companies, the finished product may vary depending on the conditions during the manufacturing process such as temperature, pressure, time, pH, amounts, etc. These conditions will vary, thus providing variation also in the final product.

Within Six Sigma exists a tool called "Components of Variation" - CoV, which can be used to identify sources of variation and quantify how much each factor contribute to the total variation. This tool has incredible many applications. Here is an example of how Components of Variation can help you understand weight variation:

What is the measurement uncertainty? How much variation can you expect within a day? Between days? Between weeks? This is a practical evaluation of weight measurements to understand and quantify variation.

To learn how to quantify and understand variation, check out Lean Techs SPC training and Evaluate Measurement training.