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Math Help - Mean & Standard Deviation

  1. #1
    TS5
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    Mean & Standard Deviation

    A steel manufacturer finds that the total quantity of raw materials used by his company each week is normally distributed with a mean of 1000 tonnes and a standard deviation of 200 tonnes. Calculate an estimate of the maximum quantity of raw materials the company is likely to use per week.

    I thought that it is 1200 because mean is the average and so with the standard deviation it would be 1000+200=1200. But, the answer accepted '1400 or 1600 tonne', how is this calculated?
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  2. #2
    Flow Master
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    Quote Originally Posted by TS5 View Post
    A steel manufacturer finds that the total quantity of raw materials used by his company each week is normally distributed with a mean of 1000 tonnes and a standard deviation of 200 tonnes. Calculate an estimate of the maximum quantity of raw materials the company is likely to use per week.

    I thought that it is 1200 because mean is the average and so with the standard deviation it would be 1000+200=1200. But, the answer accepted '1400 or 1600 tonne', how is this calculated?
    Obviously they decided to accept \mu + 2 \sigma and \mu + 3 \sigma as well.

    The question is actually too vague to give a definitive answer to. I'd suggest the justification of the answer is more important than the actual answer itself.
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