As the margin of error (or precision) of a binary proportion depends on the estimate, we also computed the relative standard error (RSE), which was below 30%.
The single population proportion formula was used to calculate the sample size considering the following assumptions: Since there is no study in Ethiopia, the proportion of women using contraceptives in the postpartum period was assumed to be 50%, 95% confidence level, 5% margin of error (absolute level of precision).
Due to that, an acceptable margin of two times the precision was fixed, that is, from −2−l+1 to 2−l+1.
Statistical power calculations showed that 20 patient records were needed to estimate the proportion that complied with the defined criteria, with a desired level of confidence of 95% and precision (margin of error) of 5% (http://www.raosoft.com/samplesize.html).html
Their planning must be thorough, ensuring a degree of precision such that the margin of error is less than 1 mm.
More satellites in coming years could reduce the margin of error to 1percentthethe precision that Gravity Probe B is aimed at.
Five Current Margin-of-Safety Graham Picks.
where Z= Z value in normal distribution tables (1.96 for 95% confidence level), p= the estimated proportion of the population that presents the characteristics (0.5 is used as a conservative value, higher or lower values yield a smaller required sample size), and H= the precision level or margin of error, expressed as decimal (10%= 0.1).
We would need 784 cases (i.e., 1.960.050.5(1 − 0.5)/(0.07/2) = 784) to achieve 95% precision and a margin of error of 7%, and assume no prior knowledge of prevalence of drug resistance, to measure prevalence of any form of drug resistance across the entire province (i.e., not enabling stratification) in each year.
Rather, since so many political observers treat poll results as a forecast, our aim is to quantify the polls' lack of precision in foretelling election outcomes, to put a real-world "margin of error" around the current polling snapshot.
