chance by odds

novice_81

Senior Member
German
Hi


In the 1930s J. B. and Louisa Rhine discovered that volunteers could guess what cards would be drawn randomly from a deck with a success rate that was better than chance by odds of three million to one. (Holographic Universe/Michale Talbot)

What does it mean "chance by odds"?
 
  • heypresto

    Senior Member
    English - England
    It's a bit awkward, I agree - it means that the odds were three million to one against the volunteers achieving a success rate this much better than chance.
     

    heypresto

    Senior Member
    English - England
    No, that's not quite right. Let's say that the volunteers achieved a 78% success rate, (when, of course, a 50% rate would be expected), then the chances of achieving this is three million to one.
     

    novice_81

    Senior Member
    German
    So the high success rate they achieved (78%, which was not expected) was like three million to one. In other words they did very well.
     
    Last edited:

    heypresto

    Senior Member
    English - England
    Yes, they did very well. At least, that's what the Rhines were claiming. I must stress that I used 78% as an example. I have no idea what the actual success rate was, or that the odds claimed against it are accurate.
     

    EStjarn

    Senior Member
    Spanish
    Those are two phrases: 'better than chance' AND 'by odds of three million to one', the latter phrase modifying the first:

    ... volunteers could guess what cards would be drawn randomly from a deck with a success rate that was better than chance.

    It is quite imprecise to say that the success rate was three million times better than chance, because we don't know the number of draws.

    The success rate of chance for a single draw is, in this case, 1:5 (there were five kinds of cards).

    For two draws, it is 1/5 x 1/5 = 1:25.

    For ten draws, it is 1:9,675,625

    For twenty draws, it is 1:95,367,431,640,625

    If we multiply those latter ratios by three million, we get the "actual" success rates: approximately 1:3 and 1:32,000,000, respectively, which are quite dissimilar ratios.

    (What I'm trying to show is that if we don't know the number of draws, we can't tell how impressive three million times better is.)
     
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