How many sample should I take….
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January 22, 2002 at 6:28 am #28577
Dr fr BdgParticipant@Dr-fr-BdgInclude @Dr-fr-Bdg in your post and this person will
be notified via email.How many sample should I take, that is the real representative for the population ?
thank’s0January 22, 2002 at 2:23 pm #71412
Tom BlackMember@Tom-BlackInclude @Tom-Black in your post and this person will
be notified via email.DR,
What do you want to know? How much confidence do you need in the answer? Sample size will be based on these. There is no one right answer.
Are you trying to characterize a population or compare two populations?
Tom Black, MBB0January 23, 2002 at 3:18 am #71424Hi,
Sample size calculation depends on the following factor.
1. Your confidence level
2. Margin of error
3. Std deviation of population ( in case of proportions it is sqrt(p*q)
Once you assumed these values calcualte the sample size as
n = Z^2 * std deviation / (error)^2
The final decision on sample size depens on the response rate. You inflate this obtained sample size as per your response rate.
hope this helps you
sridhar
0January 24, 2002 at 3:21 am #71451
HelpfulParticipant@HelpfulInclude @Helpful in your post and this person will
be notified via email.A couple of helpful notes on the above (good) reply. The standard deviation is supposed to be squared also. n= Z^2*sigma^2/E^2. Also, the last concern is “risk” that you have to consider. If you are producing heart pacemakers… you may want to do 100% testing.
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