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MEI S3 June 2012 paper question about sampling- don't understand the mark scheme Watch

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    http://www.mei.org.uk/files/papers/s3_june_2012.pdf

    question 2 a i --the ms says "Because the sampling process might be destructive"

    what do they mean by 'destructive'?

    question 2 a iii --the ms says "A random sample … enables proper statistical inference to be undertaken …… because we know the probability basis on which it has been selected"

    Probably basis on which it has been selected!?

    i don't understand what they mean
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    Help:dontknow::dontknow:
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    (Original post by freakynerdlol)
    http://www.mei.org.uk/files/papers/s3_june_2012.pdf

    question 2 a i --the ms says "Because the sampling process might be destructive"

    what do they mean by 'destructive'?
    Suppose you want to work out the average time a light bulb will last for. You take a sample, you let them burn for as long as possible, you measure the average time before they burn out. That's destructive testing - you obviously couldn't test the whole population because you'd have no light bulbs left to sell, so you test the sample and draw an inference about the whole population.
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    (Original post by davros)
    Suppose you want to work out the average time a light bulb will last for. You take a sample, you let them burn for as long as possible, you measure the average time before they burn out. That's destructive testing - you obviously couldn't test the whole population because you'd have no light bulbs left to sell, so you test the sample and draw an inference about the whole population.
    Thats amazing thank you! Mind explaining the second bit to me as well?

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    (Original post by freakynerdlol)
    Thats amazing thank you! Mind explaining the second bit to me as well?

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    Tbh that second bit sounds like waffle to me - if you forced me to guess I'd say that all they mean is that because the sample has been conducted randomly then we know there's no inherent bias in it
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    (Original post by davros)
    Tbh that second bit sounds like waffle to me - if you forced me to guess I'd say that all they mean is that because the sample has been conducted randomly then we know there's no inherent bias in it
    Thank you:yy::yy:

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