[Phys-L] Re: Reaction Time (was Re: Human Error?)

["Spagna Jr., George" <gspagna@RMC.EDU>]

John wrote:

-----Original Message-----
From: John Mallinckrodt [mailto:ajm@CSUPOMONA.EDU]
Sent: Friday, April 29, 2005 8:40 PM
To: PHYS-L@LISTS.NAU.EDU
Subject: Reaction Time (was Re: Human Error?)


> If reaction time is genuinely a source of error in such experiments
> then you need to go back to the drawing board and redesign the
> experiment.  Reaction time can only affect such measurements if, for
> instance, a) you let your partner drop the ball while you run the
> stopwatch AND you insist that your partner give you no warning or b)
> you consciously refuse to watch the ball as it drops and wait for the
> sound of the ball hitting the floor before stopping the watch.

> Of course there will be variations in the times obtained from
> successive time trials, but I maintain that they have essentially
> nothing to do with the phenomenon that is properly called "reaction
> time."

Typical reaction times are on the order of .25 s; the stopwatches we use
display precision on the order of +/- 5 ms.  I suggest to my students
that claiming the instrumental limit as the uncertainty of their
measurement is unreasonable, especially for a single trial.  Repeated
trials characteristically show a standard deviation consistent with
reaction time, rather than the stopwatch's displayed precision.

********************************************
 "The wise person doesn't give the right
 answers, but poses the right questions."
                           - Claude Levi-Strauss
********************************************

Dr. George Spagna
Chair, Physics Department
Randolph-Macon College
P.O. Box 5005
Ashland, VA 23005-5505

phone: (804) 752-7344
fax: (804) 752-4724
e-mail: gspagna@rmc.edu
http://faculty.rmc.edu/gspagna
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