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    'The time Y minutes to install a gas meter has a mean of 37 and a standard deviation of 25.

    Explain why Y is unlikely to be normally distributed.'

    The mark scheme answer is:

    'mean - (2 or 3) x standard deviation = 37 - (50 or 75)

    <0 --> likely negative times'

    Can someone explain the answer please?
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    (Original post by SherlockHolmes)
    'The time Y minutes to install a gas meter has a mean of 37 and a standard deviation of 25.

    Explain why Y is unlikely to be normally distributed.'

    The mark scheme answer is:

    'mean - (2 or 3) x standard deviation = 37 - (50 or 75)

    <0 --> likely negative times'

    Can someone explain the answer please?

    Hi, I'm not really sure but anyway I think: the standard normal distribution has a mean of 0 and standard deviation of 1 and it's spread across 3 standard deviations either side so 0 to 3 & 0 to -3 now here if the mean is 37 then the standard deviation to the left will go to ( 25 x 3 ) = 75 but because it's to the left it will be -75 & you can't get a time of -75 mins? :confused: Again I'm not sure but that's what I think
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    (Original post by Fortitude)
    Hi, I'm not really sure but anyway I think: the standard normal distribution has a mean of 0 and standard deviation of 1 and it's spread across 3 standard deviations either side so 0 to 3 & 0 to -3 now here if the mean is 37 then the standard deviation to the left will go to ( 25 x 3 ) = 75 but because it's to the left it will be -75 & you can't get a time of -75 mins? :confused: Again I'm not sure but that's what I think
    Ah I see - that sounds right. Thanks for the help
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    (Original post by SherlockHolmes)
    Ah I see - that sounds right. Thanks for the help

    Your welcome
 
 
 
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