Scientists are routinely cherry-picking and, in some cases, altering the results of clinical studies to present the findings they want, a study by academics at Oxford University shows.
http://www.theage.com.au/articles/2004/05/31/1085855496939.html

The research, which assessed the published results of more than 100 scientific trials, also found that inconvenient findings were often not disclosed to the public. In several cases, the stated purpose of the trial was altered as it progressed so that acceptable findings, rather than inconvenient results, could be published.