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January 28th, 2019, 09:24 AM  #1 
Newbie Joined: Jan 2019 From: California Posts: 3 Thanks: 0  Please help with math
A researcher is studying a population of bats in which 16% of the population has a certain trait. The researcher wants sampling distribution with a standard deviation that is less than 2%. Which sample sizes could the researcher use? Select all that apply : n=200 n=300 n=400 n=500 
January 28th, 2019, 09:48 AM  #2 
Senior Member Joined: Sep 2015 From: USA Posts: 2,549 Thanks: 1399 
What they probably want you to do is note that $\sigma_p= \sqrt{p(1p)}$ Then with a sample of size $n$ $\sigma = \dfrac{\sigma_p}{\sqrt{n}}$ i.e. $\sigma = \sqrt{\dfrac{p(1p)}{n}}$ I'll let you put your number, $p=0.16$, in and solve for $n$ such that $\sigma < 0.02$ 
January 30th, 2019, 10:10 AM  #3 
Newbie Joined: Jan 2019 From: California Posts: 3 Thanks: 0 
Can I please get the answer? I still don't get how.
Last edited by skipjack; January 31st, 2019 at 02:33 AM. 
January 30th, 2019, 10:21 AM  #4  
Math Team Joined: May 2013 From: The Astral plane Posts: 2,266 Thanks: 934 Math Focus: Wibbly wobbly timeywimey stuff.  He already told you. Quote:
Dan Last edited by skipjack; January 31st, 2019 at 02:34 AM.  

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