Design of Experiments FAQ's
Frequently asked questions about Design of Experiments.
| Software FAQ's |
I
get a message saying that the X'X matrix is singular. What's wrong?
I
get a message saying that the log condition number is greater than 15. What's wrong?
How can I get my
b-coefficients into Excel?
Why doesn't my software
recognize my replicates?
What is Gosset?
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|
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| When you see this error, it means you don't have enough data for the model you have
chosen. Perhaps you originally chose a simpler model and forgot. Maybe you were unable to
collect data for every trial in your design. Perhaps some data was entered incorrectly. |
| To eliminate this error, you will have to use a simpler model or collect more data. |
|
|
| When you see this error, it means you don't have enough data for the model you have
chosen. Perhaps you originally chose a simpler model and forgot. Maybe you were unable to
collect data for every trial in your design. Perhaps some data was entered incorrectly. |
| To eliminate this error, you will have to use a simpler model or collect more data. |
|
|
| In STATISTICA: 1. Create a table with
the b-coefficients. In STATISTICA 6.0 you can do this by selecting the ANOVA/Effects
tab and clicking the Regression Coefficients button.
2. Highlight the b coefficients. Choose Edit \ Copy.
3. Paste them into your Excel Spreadsheet.
In STRATEGY: (Thank you Ed Vawter!)
1. Run your regression.
2. Find the b-coefficients table and highlight it all.
3. Choose Edit \ Copy.
4. Paste into your Excel Spreadsheet.
5. in Excel, choose Data \ Text to Columns... \ Select Fixed width
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| DOE software looks at all of the decimal places of a trial level. If even one digit is
different, or missing, the software will count it as a different trial. To avoid this
problem, cut and paste your replicates rather than typing them in. |
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| Gosset is the consummate program for generating Optimal
experiment designs. |
| Gosset allows you to specify various factor types, including process, mixture,
discrete, and restricted, in the same experiment. |
| It allows you to specify constraints on your experiment -- limitations that would
prevent some trial from running. This allows you to create designs that don't ask you to
run trials that are impossible. |
| It allows you to augment existing data. Tell Gosset the trials you already have and it
will tell you what you need to run to turn this data into a good experiment design. |
| It allows you to specify designs in blocks to eliminate the effects of nuisance
factors. |
| Gosset allows you to specify the Optimality of your design. |
| You can learn to use Gosset in your work in the workshop, Creating
Custom Experiment Designs. |
