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    allabout grey's Avatar
    allabout grey Posts: 4, Reputation: 1
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    #1

    Mar 29, 2009, 02:29 PM
    Margin of error. Confidence level
    1.Use margin of error, confidence level, and standard deviation to find the minimum sample size required to estimate an unknown population mean.

    Margin of error: $124, Confidence level; 99%, σ = $560


    2.Find the margin of error for 95% confidence interval used to estimate the population propprtion.

    In a clinical test with 2333 subjects, 50% showed improvement from the treament.



    Thank, I'm having a hard time figure how to get the answers here.
    galactus's Avatar
    galactus Posts: 2,271, Reputation: 282
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    #2

    Mar 29, 2009, 04:55 PM
    Quote Originally Posted by allabout grey View Post
    1.Use margin of error, confidence level, and standard

    deviation to find the minimum sample size required to estimate an unknown population mean.

    Margin of error: $124, Confidence level; 99%, σ = $560
    Do you have a stats book? If so, this formula should be in there:



    You are given all the necessary info. E is the margin of error. You should know what sigma and z are. Look up z for a 99% CI in the z table.


    2.Find the margin of error for 95% confidence interval used to estimate the population proportion.

    In a clinical test with 2333 subjects, 50% showed improvement from the treatment.

    Proportions has a minimum sample formula as well.



    You have all you need to find E.
    allabout grey's Avatar
    allabout grey Posts: 4, Reputation: 1
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    #3

    Mar 30, 2009, 04:38 PM
    Quote Originally Posted by galactus View Post
    Do you have a stats book?. If so, this formula should be in there:



    You are given all the necessary info. E is the margin of error. You should know what sigma and z are. Look up z for a 99% CI in the z table.





    Proportions has a minimum sample formula as well.



    You have all you need to find E.

    Thank you, I figure the 1st one. I still confused about p and do i use 0.25 for q?
    galactus's Avatar
    galactus Posts: 2,271, Reputation: 282
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    #4

    Mar 31, 2009, 06:14 AM

    No, p+q=1. If p=.5, then what does q have to be?

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