In many cases people are expected to write abstracts several months in advance, I had to write the abstract for my 1st poster at a major conference before I had actually done any of the experiments for it.
This has been my experience also.
In fact I have just submitted an abstract , for 2006 conference of Plasma Spectrochemistry, to be held next January. It may be only for a poster but it could be a full fledged presentation. I just don't know yet. Only the very basic work has been done on the research side of things at this stage so the final poster/presentation could well be much different than the preliminary abstract.
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