# Sample Size Calculation - Proportions

Sample Size Calculation - Proportions

This Demonstration uses a normal approximation to the binomial distribution to estimate the minimum sample size, , for detecting a change in the proportion of a population with a particular characteristic (the proportion defective, for example). The sample size, , needed to detect a change of size in the proportion defective, at a confidence level of and with a power of depends on , , , and whether the test is one-sided or two-sided. To compare various sampling approaches, you can vary (the type I risk), (the type II risk), (the minimum size of change to be detected), as well as (the known, or estimated, proportion defective in the population). Note that . In many practical cases, the proportion defective is not known, but is estimated from prior sampling or experience.

n

n

δ

1-α

1-β

δ

α

β

α

β

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p

q=1-p