No test that determines probability is distribution free. They just use less restrictive distributions. The assumptions are that the observations are independent and the marginal distribution is fixed. Under the null hypothesis, all outcomes are equally likely, i.e. it's a random process.
Paul R. Swank, Ph.D. Professor, Developmental Pediatrics Medical School UT Health Science Center at Houston -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Teresa from Oregon Sent: Tuesday, December 03, 2002 6:20 PM To: [EMAIL PROTECTED] Subject: Fisher's exact test I was doing a little mental calisthenics today and got myself confused about how this test is calculated. My (perhaps naive) understanding is that all potential sets of results from, say, a 2x2 table are calculated and then the exact probability of the actual observed result occurring simply by chance is determined. This is why there is no associated test statistic, just p. My question is: If the test is distributionless, wouldn't the probability of all unique results be equal? Or...put another way...Is Fisher's exact one of those sneaky nonparametrics that really does rely upon an underlying distribution? Thanks. . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . ================================================================= . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
