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Strategies & Market Trends : ahhaha's ahs -- Ignore unavailable to you. Want to Upgrade?

To: GraceZ who wrote (568)	12/9/2000 4:22:30 PM
From: M. Frank Greiffenstein	Read Replies (1) \| Respond to of 24758

Well, ahhaha is correct that an odds ratio is different than a probability. Take it from somebody trained in epidemiology. Odds ratios state a mutltiplicative relationship between two outcomes but they are not necessarily exhaustive of all possible occurrences. Taking a published study I just read, the odds ratio of developing post traumatic stress disorder after a car crash if you had a past diagnosis of PTSD is 10:1. This means you are ten times more likely to develop it than somebody without PTSD before their car crash. But it doesn't mean that 10 out of every eleven car crash victims had PTSD before their car crashes. If the probability of developing PTSD after a car crash without premorbid PTSD is .02 and prob of getting it again if you had it is .20, the odds ratio is 10:1, even though you have depleted only 22% of all MVA victims. Incidentally, when you read about disease prevalence in the newspapers, statistics are usually stated in terms of odd ratios, e.g., if you eat an apple treated with agar, you are 1.5 or 50% more likely to get stomach cancer." Of course, people get frightened and call their congressmen. But the astute reader should always ask "1.5 times what?". If the prevlance is 1 per million, that would mean 1.5 per million people who ate apgar are diagnosed with cancer. And that is the problem with odds ratios: They artificially inflate differences at extremes of a distribution. Doc Stone

To: GraceZ who wrote (568)	12/10/2000 1:34:50 PM
From: ahhaha	Read Replies (2) \| Respond to of 24758

Bilow already corrected that error on my part. I should have been precise and formal like everyone else out there. In 1970 I heard Clark say that HAL = Heuristic Algorithmic Language which is somewhat oxymoron because heuristic means informal and lacking of rigor whereas algorithmic is formal and non-creative. Clark later apparently changed this to just Heuristic ALgorithmic which is grammatically nonsensical. "Look up in the sky. It's a bird, it's a plane, no, it's an ALgorithmic". Clark went down the drain as he got older which was clear when he let a patzer write a sequel to the "City and the Stars". So we can't tell what he was saying. If he was saying what I heard him say, 'Griff had the right calculation. Unless one makes the assumption that two letters are taken at the same time which compacts the possibilities one can't reach Clark's calculation. That requires one believe a white man and many know white man speak with forked tongue.