I'm a mathematician who has also worked in marketing, so I am familiar with this term from both worlds.

The correct translation *is* "monadic," (as already suggested by Marina.M) but not for the reason she cited. Her citation was from a different field, Mathematics and Computer Science, where "monad" is a very common term referring to an operator or function which takes only one argument (in this sense, "monadic" = "unary"), or specfically in Category Theory (a field in Mathematics), where it refers to a particular type of functor.

So *none* of the uses of the term "monad" on the following wiki page are applicable to marketing tests:

http://en.wikipedia.org/wiki/Monad

Now, let's find a citation from the world of marketing tests, where "monadic" simply means a product test involving just one product:

http://www.burke.com/Services/CMR/services.cfm?id=15

***Monadic*** Product Tests. In ***monadic*** testing, a respondent tests a single product and provides an evaluation of that product. Data collected typically includes variables such as purchase interest and ratings on attributes. If there is more than one product to be tested, matched groups of respondents would test each product, with the data collected from each group being compared to each other.

Paired Comparison Product Tests. In a paired comparison test, respondents use two products in sequence, with no questioning in between. After both products have been used, they are asked to rate each and state a preference. Because questions are not asked until both products have been tried, the evaluation of a product is always in the context of a comparison to the other.

There are other comparative type test designs, such as triangle and triad tests (evaluating three products in sequence), as well as variations such as repeat paired comparison designs, but they are all essentially modifications of comparative testing designs. Generally, however, when deciding upon the appropriate test design, the first decision must be "***monadic***" or "comparative"?

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This is the example of "monadic" you were looking for!