On Mar 19, 2010, at 11:23 AM, Miles Jackson wrote:
> I'm making no heroic assumptions; I'm just passing along what every
> statistics student learns in their first course on probability. If
> you randomly assign people to two groups, the potential confounds
> are also randomly distributed across the groups, and it is not
> plausible to argue that the groups systematically differ. Really,
> it's Probability 101. Random assignment to experimental condition
> is a very powerful and rigorous technique to control confounds here
> (including any potential confounds you and I are not clever enough
> to imagine!).
You could argue that the group sizes are too small for true randomness to prevail. What's the thinking on this in psychology? How big a group do you need?
Doug