If the head side is larger (heavier?), shouldn’t it come up tails? Jim
Jim Clark Professor & Chair of Psychology University of Winnipeg 204-786-9757 Room 4L41 (4th Floor Lockhart) www.uwinnipeg.ca/~clark<http://www.uwinnipeg.ca/~clark> From: John Kulig [mailto:[email protected]] Sent: Monday, March 02, 2015 8:10 AM To: Teaching in the Psychological Sciences (TIPS) Subject: Re: [tips] Are coin tosses random? As a practical demo of a related issue, stand a few pennies on their edge (I would alternate which side heads is on) on a table and shake or tap the table and most will come up heads due to the fact that the head side of a penny is ever so slightly larger than the tail side, hence has a very slight preexisting tilt (that's what I have read .. I have not microscopically examined them). But I have done it with pennies and if done carefully it is very easy to demonstrate p<.05 :-) a value very different that 50%. A physicist friend once explained how coins spun have a bias (slight) for tails. And I have usually regarded random as ignorance ,,, ========================== John W. Kulig, Ph.D. Professor of Psychology Coordinator, Psychology Honors Plymouth State University Plymouth NH 03264 ========================== ________________________________ From: "Wuensch, Karl L" <[email protected]<mailto:[email protected]>> To: "Teaching in the Psychological Sciences (TIPS)" <[email protected]<mailto:[email protected]>> Sent: Sunday, March 1, 2015 11:01:21 PM Subject: RE: [tips] Are coin tosses random? Philosophically this issue is more important. Does “random” just mean ignorance of the mechanisms involved in determining the outcome (and ignorance of the current states of those mechanisms). In the absence of ignorance, would anything be random? Cheers, [Karl L. Wuensch]<http://core.ecu.edu/psyc/wuenschk/klw.htm> From: Jeffry Ricker, Ph.D. [mailto:[email protected]]<mailto:[mailto:[email protected]]> Sent: Sunday, March 01, 2015 3:37 PM To: Teaching in the Psychological Sciences (TIPS) Subject: Re: [tips] Are coin tosses random? On Feb 28, 2015, at 6:28 PM, Jim Clark <[email protected]<mailto:[email protected]>> wrote: One lesson I take away from Jeff`s original post (i.e., that even a simple coin toss probability is a challenge to determine) is that we should not worry too much by such minutia as whether all the abstract assumptions for statistical tests are met. The real world is so messy that such contributions to the correctness of our conclusions are probably minimal and in an uncertain direction. Yes, that's an excellent point. I also was thinking about several other issues that these studies might help to clarify for students. One is the issue of internal versus external validity (and yes, ecological validity also could be mentioned, although that isn't what concerns me with coin tossing). Based on what I was able to understand of their conclusions, both groups of researchers seemed to be stating that their findings had high internal validity, but they didn't think they would generalize to the types of situations in which coins typically are tossed. I thought this would be an easy–to–understand example to use when I discuss validity—as long as I leave the math out!!! Best, -- --------------------------------------------------------------------------------- Jeffry Ricker, Ph.D. Professor of Psychology --------------------------------------------------------------------------------- Scottsdale Community College 9000 E. Chaparral Road Scottsdale, AZ 85256-2626 Office: SB-123 Phone: (480) 423-6213 Fax: (480) 423-6298 --- You are currently subscribed to tips as: [email protected]<mailto:[email protected]>. 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