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May 14th, 2016, 01:20 PM  #1 
Member Joined: May 2016 From: Ireland Posts: 96 Thanks: 1  maths statistics
hi i cant solve this Assume the duration of human pregnancies can be described by a normal model with a mean 270 days and a standard deviation of 15 days (i) using the empirical rule write down the 95% confidence interval for the mean pregnancy duration (ii)At least how many days should the upper quartile of pregnancies last 
May 22nd, 2016, 02:48 AM  #2 
Senior Member Joined: Aug 2012 Posts: 229 Thanks: 3 
Hey markosheehan. Do you understand 95% has rougly + 1.96 standard deviations from the mean? (for a Normal distribution that is)? 

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