Central composite design software plus#

You need the experimental region to be big enough to observe the trends in the response surface.

Central composite design software plus#

I'd suggest running a first-order experiment (just the four corners plus a few center points) over a rectangle comprising, say, the middle third or middle half of the range of each variable. So, what to do? This really depends on how much error there is and you may not know much about that until you have some data. There is also not all that much data in one CCD, but (1) says that if indeed the actual surface is second-order, then a CCD over the whole region of operability makes the best use of that small amount of data. The surface may not be second-order and may not be well approximated by a second-order model over that wide a range. Note that (2) answers 'no' to your first question - one CCD over the whole region is not enough to find the maximum with any assurance. All this said, you could counteract (1) by replicating - i.e., run two or more CCDs on the selected region so that is an option as well. Notice that (1) says you want a far-ranging experiment, and (2) says you want a smaller scope. But if the experimental region is too large, then the second-order model may no longer be very useful. That model is useful if the experimental region is small enough that the second-order equation is a reasonable approximation to the true response surface. CCDs are great for estimating second-order (quadratic) surfaces. The larger the experimental region, the more accurately we are able to estimate the equation of the response surface, assuming that our model is correct.ДЄs has been stated by GEP Box and others, all models are wrong, but some are useful. Here are two important things to consider:ДЄs in all statistics contexts, we assume that data are measured with error.