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Math Help - Systematic vs. Random sampling

  1. #1
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    Systematic vs. Random sampling

    "Every twenty-fifth person who subscribed to a weekly news magazine was contacted by market researchers to complete a survey of opinions regarding the magazine's contents. The researchers were applying the technique known as:"

    The answer is random sampling.

    I think it's systematic sampling because you're using a system (every 25th person). I'm having trouble explaining this (english isn't my first language) so how would I go about doing this? (having trouble putting into words).
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  2. #2
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    Re: Systematic vs. Random sampling

    Hey snypeshow.

    The question that needs to be asked is whether its every 25th person in time or whether you pick one person for every 25 overall.

    The answer to the above will make a huge difference to the final sampling scheme.
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    Re: Systematic vs. Random sampling

    I posted the question verbatim, so from reading the question, I'm assuming "25th" means "not 24th, nor 26th", so to be selected as the 25th person, it's dependent on if the 24th person has been chosen or not, therefore it isn't mutually exclusive.

    For a sample to be random, the odds have to be mutually exclusive from all other events, which "25th" doesn't fit. However if it was 1 in 25, that would mean mutual exclusivity of the 1 individual from the sample of 25

    That would be my reasoning. Would that be correct?
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  4. #4
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    Re: Systematic vs. Random sampling

    If the chances of any person being selected are exactly the same (even given the selection history of past people), then it is a real pure random sample.
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