Guest post by Bradley Jones
Almost a hundred years ago R. A. Fisher‘s boss published an article espousing OFAT (one factor at a time). Fisher responded with an article of his own laying out his justification for factorial design. I admire the courage it took to contradict his boss in print!
Fisher’s argument was mainly about efficiency – that you could learn as much about many factors as you learned about one in the same number of trials. Saving money and effort is a powerful and positive motivator.
The most common argument I read against OFAT these days has to do with inability to detect interactions and the possibility of finding suboptimal factor settings at the end of the investigation. I admit to using these arguments myself in print.
I don’t think these arguments are as effective as Fisher’s original argument.
To play the devil’s advocate for a moment consider this thought experiment. You have to climb a hill that runs on a line going from southwest to northeast but you are only allowed to make steps that are due north or south or due east or west. Though you will have to make many zig zags you will eventually make it to the top. If you noted your altitude at each step, you would have enough data to fit a response surface.
Obviously this approach is very inefficient but it is not impossible. Don’t mistake my intent here. I am definitely not an advocate of OFAT. Rather I would like to find more convincing arguments to persuade experimenters to move to multi-factor design.
Related: The Purpose of Factorial Designed Experiments – Using Design of Experiments – articles by R.A. Fisher – articles on using factorial design of experiments – Does good experimental design require changing only one factor at a time (OFAT)? – Statistics for Experimenters
Problems with Management and Business Books
We really need to change how we improve the practice of management. Far too often management strategies are just the latest fad from some new book that successfully marketed an idea. The marketing effectiveness of a book, or consultant, has very limited correlation to their ability to improve management, in my experience. It is often true that they make very good keynote speakers, however. So if you want an entertaining keynote speaker looking at the authors of the best selling business books may make sense. But if you want to improve management, I don’t see much value in doing so.
Year after year we have the same basic business books repackaged and marketed. They present a magic bullet to solve all your problems. Except their bullet is far from magic. Usually it does more harm than good.
They amazingly oversimplify things to make their bullet seem magic. This also fails miserably in practice. There are usually not good management options that are simple and easy. Usually the answers for what should be done is a lot of “it depends,” which people don’t seem to like.
Authors fail to place their book (or their trademarked strategy they hope turns into a movement/fad) in the appropriate context. Most books just take a few good ideas from decades old practices add a new name and leave off all references to the deep meaning that originally was there. I guess quite often the authors don’t even know enough about management history to know this is the case; I guess they really think their minor tweak to a portion of business process re-engineering is actually new. This also would make it hard for them to place their ideas within a management philosophy.
On a related note, I find it interesting how different the lean manufacturing and six sigma communities are online (and this has been going on for more than a decade). One of the problems with six sigma is there is so little open, building on the practices of six sigma. Everyone is so concerned with their marketing gimmick for six sigma that that don’t move forward a common body of work. This is a serious problem for six sigma. Lean manufacturing benefits hugely from the huge community of those building openly on the body of knowledge and practice of lean. You can find 10 great lean manufacturing blogs without trouble. You will have difficulty finding 3 good six sigma blogs (and even those spend most of the time on other areas – often lean thinking).
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