I agree with Martinique to some extent, but I feel that a clearer explanation is needed:

“Double blind” and “double dummy” are two different concepts.

Double blind = neither the investigator/research team nor the subject know whether the subject is taking the active drug or placebo.

“Double dummy” refers to the technique used, and it means that the “blind” approach is also extended to the pharmaceutical form of the investigational drug, as defined below:

Double dummy refers to a procedure that is used when the two treatments are so obviously different that it would undermine the whole double blind idea.
For instance, you want to test a medication that is in capsule form to a medication that is a liquid. Obviously, the subject would know what they were getting if just given one of the medications. So each subject receives both treatments with groups structured as follows:
Group One: active capsule, placebo liquid
Group Two: placebo capsule, active liquid
Group Three: placebo capsule, placebo liquid.
http://www.pballew.net/arithme2.html

Double Dummy: A technique for retaining the blind when administering supplies in a clinical trial, when the two treatments cannot be made identical. Supplies are prepared for Treatment A (active and indistinguishable placebo) and for Treatment B (active and indistinguishable placebo). Subjects then take two sets of treatment; either A (active) and B (placebo) or A (placebo) and B (active). http://www.actmagazine.com/appliedclinicaltrials/article/art...

Hope this helps.


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Note added at 3 hrs 4 mins (2005-06-04 15:33:01 GMT)
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I have three suggestions:
1. Try to find out whether there is an accepted and widely used Chinese equivalent for this clinical study term.
2. Leave “double dummy” in English (can you do this in a Chinese text?:))– medical professionals will probably understand the concept. To be on the safe side, you can insert the explanation in Chinese in brackets.
3. Use an acceptable Chinese term for “dummy”, but if this hasn’t been used before in this context, I would still insert the explanation in Chinese and/or \"double dummy\" in English in brackets.
You could perhaps translate it as \"double placebo\", as defined below:
double placebo - A placebo having two different shapes or forms, eg, a tablet and a capsule, as needed in a double placebo treatment design; also double dummy placebo. rt: single placebo, multiple placebo.
http://www.jhucct.com/clm/gppps/Mak.pdf