



 
Hi Rae, My understanding of this question is that someone has reported
And you want to determine the sample size the researcher used. You know that 18 out of 20 is a 90% confidence interval, z_{0.05} = 1.645 and the sample proportion was 0.75 so the calculation to obtain an error bound of ± 0.02 was Squaring both sides and solving for n gave me n = 1268.4. Harley  


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