【题目】DOE离散变量伪中心点的设置

本帖最后由 focuscon 于 2010-9-28 20:34 编辑

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沒有專門去看,謝謝你的提示! 人有時候就是太笨找不到門路. Minitab幫助文件確實是個好資料!
The way Minitab adds center points to the design depends on whether you have text, numeric, or a combination of text and numeric factors. Here is how Minitab adds center points:

· When all factors are numeric and the design is:

• Not blocked, Minitab adds the specified number of center points to the design.

• Blocked, Minitab adds the specified number of center points to each block.

· When all of the factors in a design are text, you cannot add center points.

· When you have a combination of numeric and text factors, there is no true center to the design. In this case, center points are called pseudo-center points. When the design is:

• Not blocked, Minitab adds the specified number of center points for each combination of the levels of the text factors. In total, for Q text factors, Minitab adds 2Q times as many centerpoints.

• Blocked, Minitab adds the specified number of center points for each combination of the levels of the text factors to each block. In each block, for Q text factors, Minitab adds 2Q times as many centerpoints.

For example, consider an unblocked 23 design. Factors A and C are numeric with levels 0, 10 and .2, .3, respectively. Factor B is text indicating whether a catalyst is present or absent. If you specify 3 center points in the Designs subdialog box, Minitab adds a total of 2 x 3 = 6 pseudo-center points, three points for the low level of factor B and three for the high level. These six points are:

5
present
.25

5
present
.25

5
present
.25

5
absent
.25

5
absent
.25

5
absent
.25


Next, consider a blocked 25 design where three factors are text, and there are two blocks. There are 2 x 2 x 2 = 8 combinations of text levels. If you specify two center points per block, Minitab will add 8 x 2 = 16 pseudo-center points to each of the two blocks.