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Again new good manuscript by Donald J. Wheeler
When analyzing data it is essential to distinguish between observational studies and experimental studies. The data may be said to have come from an observational study when they arise as a side effect of some continuing operation or on-going process.
In contrast to this, when a series of operations are carried out specifically in order to obtain specific data, those data may be said to have come from an
experimental study. Virtually all data can be said to come from either an observational study or an experimental study.

Clearly, process behavior charts were intended for use with observational studies. Since it will generally be much easier to obtain data as a side effect of operations, this alone makes the process behavior chart one of the most important tools in your data analysis tool kit.



However, as is shown in the several of my books, process behavior charts may also be used with experimental data. In fact, they will often be the only analysis technique that will reveal certain aspects of your data (such as a lack of homogeneity where the data should be homogeneous). However, by the very nature of an experiment, experimental data will be collected under two or more conditions. This characteristic of experimental data places restrictions on how the data may be analyzed.

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