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September 9th, 2013, 11:33 PM  #1 
Newbie Joined: Sep 2013 Posts: 1 Thanks: 0  New to statistics  need help!
Hi everyone, I've recently started studying maths again at university and am struggling to answer this probability equation. The average birth weight of a bottlenose dolphin calf is 22kg. Assuming these birth weights follow a normal distribution with a standard deviation of 3kg answer the following question 15 newborn calves have been observed by Rosie, a bottlenose dolphin researcher at Shark Bay. Assuming these observations are independent, find the probability that the average birth weight for these 15 calves is higher than 23kg. I'm not sure if I'm meant to be using a normal distribution equation or somehow incorporating the central limit theorem with the standard error. If anyone could help me solve this ASAP I would greatly appreciate it! Thanks so much for all your help 
September 12th, 2013, 05:21 PM  #2 
Senior Member Joined: Aug 2008 From: Blacksburg VA USA Posts: 345 Thanks: 6 Math Focus: primes of course  Re: New to statistics  need help!
I am unsure of your familiarity. The "bell" curve has defined properties in terms of %population, in terms of distance away from the mean (in terms of std dev.). First you must know the "line" in these terms. Your line is (2322)/3 std deviations ie 0.333 std dev above mean. The precomputed table reports % population above,below or within std dev limits. Your population size is 15. Numerically (ideally), as we expect half/50% above and below/50% mean, what does this tell you about the group's "avg" falling above the mean ? You can reply here and others can detail more depending on where your understanding is at. 

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