Originally Posted by heehaww
Especially question a claim made about something not in the author's area of expertise (I wouldn't go to a psychologist to learn about mathematics, nor to a mathematician to cure my craziness). But I think Monteroy's explanation is likely, and you didn't read carefully enough. Maybe you only saw the data and only thought of 1 possible interpretation (which happened to be the wrong one).
I'm a psychologist and people come to me all the time for statistical questions. Statistics and research methods is pretty much a requirement for any BA/BS in psychology in US (exceptions may apply, but I personally would suggest transferring to another university to get a psych degree than to get one without these topics covered). My minor area of study for my Ph.D. was in quantitative psychology. That being said, psychology is much more about applied statistics than about probability theory / mathematics (which no doubt explains my frequent mistakes on this forum about combinations and pure probability problems).
For what it is worth, I doubt this is something that was read in a psychology class. I think the most likely explanation is that either 1) the student remembered what the instructor said incorrectly or 2) the instructor got it wrong. The reason for this that most students don't read (my students always find it amazing when I tell them about a neat study that was in the book; if they were reading they should be bored by it).
Further, despite (research) psychologists have reasonable training in quantitative issues, many of them still suck at it, which makes #1 plausible. #2 is also plausible because...well, see the scores on my exams for the evidence against student memory. I'd rate "didn't read carefully enough" as the third possibility and "book error" as an outside 4th.
So in order of likeliness:
1) Student misheard/misunderstood/misremembered the lecture
2) Instructor said it incorrectly
3) Student misread/misremembered book
4) Book is in error.