Obvious ethical considerations aside, I’ve never understood scientific fraud from a practical point–it’s a ton of work. You might as well do more experiments. Diederik Stapel (boldface mine):
Sitting at his kitchen table in Groningen, he began typing numbers into his laptop that would give him the outcome he wanted. He knew that the effect he was looking for had to be small in order to be believable; even the most successful psychology experiments rarely yield significant results. The math had to be done in reverse order: the individual attractiveness scores that subjects gave themselves on a 0-7 scale needed to be such that Stapel would get a small but significant difference in the average scores for each of the two conditions he was comparing. He made up individual scores like 4, 5, 3, 3 for subjects who were shown the attractive face. “I tried to make it random, which of course was very hard to do,” Stapel told me.
Doing the analysis, Stapel at first ended up getting a bigger difference between the two conditions than was ideal. He went back and tweaked the numbers again. It took a few hours of trial and error, spread out over a few days, to get the data just right….
Stapel had a student arrange to get the mugs and M&M’s and later load them into his car along with a box of questionnaires. He then drove off, saying he was going to run the study at a high school in Rotterdam where a friend worked as a teacher.
Stapel dumped most of the questionnaires into a trash bin outside campus. At home, using his own scale, he weighed a mug filled with M&M’s and sat down to simulate the experiment. While filling out the questionnaire, he ate the M&M’s at what he believed was a reasonable rate and then weighed the mug again to estimate the amount a subject could be expected to eat. He built the rest of the data set around that number. He told me he gave away some of the M&M stash and ate a lot of it himself. “I was the only subject in these studies,” he said. [study not published]
I’m convinced that scientific fraud is only partially born from desperation. In the second example, it probably would have been as much work to actually run the experiment–though he would run the ‘danger’ of not getting a significant result. At some level, I think you have to want to do this, perhaps even need to do this.