Standard deviation for proportions

[ZSs]

Hi,,,can u please explain me how to calculate standard deviation and standard error for a binomial distribution when you have several samples?

 

For exapmple,

I don't know the population size. I take a sample of 10 and check for a particular characteristic. Let's say number of successes for this sample is x. So the proportion of successes is x/n. Then I repeat this process for 3 times. That means I take 3 samples. Then I'll calculate the mean for these 3 samples. So how do I calculate standard deviation or standard error for this mean value?

 

Eg: Sample 1 => x/n = x/10 =3/10 =30%

 

      Sample 1 => 30% +- a

      Sample 2 => 32% +-b

      Sample 3 => 32% +- c

 

     Mean = 31.33% +-d

 

 

How do I calculate a,b,c and d? And what if I have different sample sizes for the three occasions? (having 10, 15, 8 instead of 10,10,10)

 

Thank you very much for your help

Edited December 14, 2013 by ZueSz

[Biostat_Assistant_Prof]

Wrong type of forum

[ZSs]

Sorry,,,