Sample Proportions Section 9.2.

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Presentation transcript:

Sample Proportions Section 9.2

p hat = X/n p hat = p p hat = [(p(1 – p)/n] If the population is much larger than the sample, the count X will follow a binomial distribution p hat = p p hat = [(p(1 – p)/n]

p hat is an unbiased estimator of p The standard deviation gets smaller as n increases

Rule of Thumb 1 Use the recipe for the standard deviation of p hat only when the population is at least 10 times as large as the sample

Rule of Thumb 2 Use the normal approximation to the sampling distribution of p hat for values of n and p that satisfy np  10 and n(1 – p)  10

Practice Problems pg. 513 #9.25-9.30