Paul, You're absolutely right. I think I'm going to go over to the College Center and conduct my own tea procedure...
Larry -----Original Message----- From: Paul Smith [mailto:paul.smith@;alverno.edu] Sent: Wednesday, November 13, 2002 8:28 AM To: Teaching in the Psychological Sciences Subject: Re: p is continuous, not dichotomous Larry Daily wrote: > Ok, I shouldn't be writing about statistics when I haven't yet had my first > cup of tea for the day... > > I wrote that p is the probability of rejecting the null when it is false. > What I *meant* to write was that p is the probability of rejecting the null > when it is, in fact, true. The rest, I think, was accurate. (running the same risk: no coffee yet...) Isn't that closer to a description of "alpha" than of "p"? Either way, I see things somewhat differently (and sorry if this sounds picky - but of course it is <grin>). We KNOW whether or not we have rejected the null hypothesis when we're done with an analysis. I don't think we're calculating probabilities of rejecting the null, or of failing to reject the null. We're calculating conditional probabilities of (finding the data we found | the null is true). That's how I'd describe "p". We set up a probability distribution representing the situation we have under the assumption that the null hypothesis is true. Then using that distribution, we find the probability of obtaining data that we in fact know that we have obtained. That probability is, again, based on the assumption that the null is true, and if that probability is sufficiently small, we find ourselves wondering if we have made a bad assumption. The assumption that we question is the one that the probability distribution described by the null hypothesis is the one that actually describes the distribution of data in the larger population. On the basis of that calculated probability of p, then, we make a decision about whether or not to reject the null hypothesis. Sorry, no insights into poetry, but here's a Dorothy Parker poem appropriate for those us folks in our first semester back from sabbatical: Dorothy Parker - The Flaw in Paganism Drink and dance and laugh and lie, Love, the reeling midnight through, For tomorrow we shall die! (But, alas, we never do.) Paul Smith Alverno College Milwaukee --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED] --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED]
