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In Reply to: RE: Levels of knowledge about cables posted by laznos on July 03, 2009 at 21:51:44
"""But would any self-respecting golden-eared audiophile ever think that the Radio Shack was better than the Cardas? No, never. Me notwithstanding. So whatever prior statistical distribution you may have used for the Cardas and Radio Shack should have included golden-eared audiophiles, which you seem to be a part of. Which means you should have used a ONE-TAILED statistical distribution in evaluating it. In other words, the idea that Radio Shack was better than Cardas should have been ruled out beforehand. So any numbers without using this directional hypothesis are wrong."""
I don't know why you are referring to this in the past tense. The test hasn't happened yet (except for two initial trials which are really part of a learning and experimental period).
I don't pre-judge that the Radio Shack is worse than the Cardas. It may be different for different test tracks. I deliberately use different music each time I try to compare trials, as I did in my initial two trials, so as to keep my ears fresh and avoid a situation where I develop expectations too easily. In the test protocol, you'll notice that I don't know the identity of A and B. I don't know how often this is done in ABX tests, but I DO NOT want to know which of A and B is the expensive cable, to be sure I'm judging on sound alone.
As for one-tailed vs two-tailed distributions, you will have to explain more. I don't follow what you wrote.
"""Next, the permutation in which A and B are randomly assigned should be generated in an unbiased manner randomly. We just have your word here that this was true."""
My friend tossed a coin.
"""Are you evaluating "A is better than B", or "A is different than B"? See above, for the difference between one-tailed and two-tailed hypotheses."""
A is different than B. That's very important. To stay open to the possibility that preferences may change depending on the music I'm using, or even the day the test is run, I only try judge that A is different than B.
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