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# S1 Normal Distribution watch

1. '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.'

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

<0 --> likely negative times'

2. (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.'

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

<0 --> likely negative times'

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? Again I'm not sure but that's what I think
3. (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? Again I'm not sure but that's what I think
Ah I see - that sounds right. Thanks for the help
4. (Original post by SherlockHolmes)
Ah I see - that sounds right. Thanks for the help

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Updated: April 4, 2013
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