5.3. Choosing an experimental design
|Planning an experiment begins with carefully considering what the objectives (or goals) are||
The objectives for an experiment are best determined by a team
discussion. All of the objectives should be written down, even the
The group should discuss which objectives are the key ones, and which ones are "nice but not really necessary". Prioritization of the objectives helps you decide which direction to go with regard to the selection of the factors, responses and the particular design. Sometimes prioritization will force you to start over from scratch when you realize that the experiment you decided to run does not meet one or more critical objectives.
|Types of designs||
Examples of goals were given earlier in
Section 5.1.2, in which we
described four broad categories of experimental designs, with various
objectives for each. These were:
Note that some authors prefer to restrict the term screening design to the case where you are trying to extract the most important factors from a large (say > 5) list of initial factors (usually a fractional factorial design). We include the case with a smaller number of factors, usually a full factorial design, since the basic purpose and analysis is similar.
|Based on objective, where to go next||
After identifying the objective listed above that corresponds most
closely to your specific goal, you can