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#1 2008-12-12 01:01:18

Prakash Panneer
Member
Registered: 2006-06-01
Posts: 110

Statistics.... Please help me...

18 people are randomly selected with a mean score of 550 and a std. dev. of 140. Find the 95% confidence interval for the population variance and std.

can you tell me how i find point estimates for population variance and standard deviation?

Thanks in advance.


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#2 2008-12-17 04:30:45

mathceleb
Member
Registered: 2008-08-27
Posts: 19

Re: Statistics.... Please help me...

Prakash Panneer wrote:

18 people are randomly selected with a mean score of 550 and a std. dev. of 140. Find the 95% confidence interval for the population variance and std.

can you tell me how i find point estimates for population variance and standard deviation?

Thanks in advance.

Prakash,

This sounds like you can use a Chi-Square Confidence interval.  We have our Sample N = 18 and our confidence percentage of 95%.  Since standard deviation is 140, squaring that gets us our variance of 19600.

Go here and plug those 3 in:

Chi-Square Confidence Interval for the Variance and Standard Deviation

This will show you every single line of math for how to determine both the variance and standard deviation confidence i nterval.  Press either button to see the math work.  You will notice about halfway down I provide a shortcut in Microsoft Excel for how to calculate some of the values on the fly if you ever need to.

Let me know if I can provide more assistance.

Last edited by mathceleb (2008-12-17 04:38:28)

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