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back to article Google offers Adwords deals - but you can't trust their numbers

Google's Adwords platform has always been something of a mystery, to put it mildly - the only certainty about it is that it makes a lot of money for Google - but nobody has caught it out using numbers which are definitely, verifiably untrue. Until now. Simples An eagle-eyed Reg reader has broken this long run of success. …

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  1. stanimir

    More marbles

    The riddle is rather trivial, so I wonder how they managed to screw the answer... or lost the count of their marbles in this particular case.

    The 1st time I read it it appeared to me blue and green marbles also had 3/5 odds to be picked and that would have made the bag sort of magic or voodoo magic. The latter would explain adwords deals nicely.

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    1. Arbee
      Reply Icon
      FAIL

      Re: More marbles

      I think it's a simple clerical error. The answer is (3*3)/(14*15), or 9/210. This simplifies to 3/70, but I think they've just simplified the denominator.

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      1. stanimir
        Reply Icon

        Re: More marbles

        @Arbee, or they are color blind and mistook red for green. :)

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      2. Flawless101
        Reply Icon

        Re: More marbles

        An unforgivable mistake.

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  2. Neil Barnes Silver badge
    Facepalm

    Insufficient data in the question...

    I sort of assumed that the marble was returned to the bag after selection, giving the slightly lower rate of (3*3)/(15*15) = 9/225 = 1/25

    Doh.

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    1. Wize
      Reply Icon

      Re: Insufficient data in the question...

      Though the chance of pulling a green marble on the second draw should be lower. You have already pulled out a blue one, so your luck favours blue.

      Well, that is how many play roulette.

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      1. Matt 21
        Reply Icon

        Re: Insufficient data in the question...

        I think that if you're Google you look in the bag and pick the colour you want. That would explain a lot about how ads work on Google:-)

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    2. Trustme
      Reply Icon

      Re: Insufficient data in the question...

      "I sort of assumed that the marble was returned to the bag after selection"

      I did the same.

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  3. Crisp

    A bag contains fifteen marbles.

    Unless you live at Mountain View.

    In which case, you've probably lost a few.

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  4. Anonymous Coward
    FAIL

    Is it just me or could the excerpt:

    'The probability of choosing a red marble from the bag is 3/5. There is an equal probability of choosing either a blue or green marble'.

    be read to mean that there is as equal a chance of getting a blue/green marble as a red one? this would mean that the actual probability would be:

    9/15 * 9/14 = 81/210

    Fail, just in case Stephen Fry comes in here and puts me right on my grammar...

    0 1
    1. ratfox
      Reply Icon
      Happy

      That would be a very special bag

      Which would allow you to have a red marble with probability 3/5, a blue marble with probability 3/5, and a green marble with probability 3/5, for a total of 9/5. Which would mean that almost every time you choose a marble, you end up choosing two at the same time!

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      1. Anonymous Coward
        Reply Icon
        FAIL

        Re: That would be a very special bag

        Exactly, which is why this is an epic combination of 'question' and 'answer' fail by Google.

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    2. stanimir
      Reply Icon

      I mentioned that was the way I read it first but it required the voodoo bag so I discounted the option.

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  5. hugo tyson
    FAIL

    I hate questions like that...

    ...precisely because they never state whether each pick is replaced before the next one. But whatever the quizmaster was thinking is "right" even though a crucial fact was kept sekrit.

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  6. Anonymous Coward
    Facepalm

    Much more complicated is their Youtube adds sign up.

    Youtube, Step 1: Sign up to Addsense on the Addsense website and come back here.

    Addsense, Step 1: Sign up using the Youtube website and come back here.

    (Still not figured out how to get an Addsense website linked to youtube, as both send you to links on the other site THAT LINK BACK!)

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  7. Alistair Swanson
    Stop

    Assumptions

    The probability of picking a red marble is 3/5 and there are 15 marbles, therefore 9 of the marbles must be red?

    How very presumptuous of people to assume that Google are wrong.

    Could the marbles be different sizes/weights/temperatures?

    Could the contents of the bag be visible so people’s preferences to colour may affect the results?

    Could not picking a marble be an option?

    This is clearly Google’s way of saying that adwords is a black box and you just need to trust them at their word.

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  8. claude191

    Google's mistake was transcription, not maths

    It looks like this problem was copied from here:

    http://www.mathplayground.com/MTV/mathtv11.html

    In this example the question is identical EXCEPT at the very end its uses a red marble instead of a green one. The result is the 9/70 as per Google's answer page.

    So they didn't plagiarise the question properly....

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