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Lecture 14

# Lecture 14 - overpaid Example 2 In a 1998 article the...

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Population Proportions Population Parameter: p - population proportion Sample Statistic: p ˆ = X where X is a binomial n random variable Sampling Distribution of p ˆ Mean µ p ˆ = p Standard Deviation σ p ˆ = q p ˆ ˆ / n where q ˆ = 1 – p ˆ The distribution of p ˆ will be approximately normal when n is large. This means we can convert to standard normal (or z) and use standard normal table for probabilities. Confidence Interval sample statistic ± z (α/2)· standard error p ˆ ± z(α/2) q p ˆ ˆ / n

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Example 1: 883 of 1014 people surveyed believed doctors and dentists charge too much. Find a 95% confidence interval for the true proportion who believe they are

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Unformatted text preview: overpaid. Example 2 In a 1998 article, the credit card industry asserted that at most 50% of college students carry a credit card balance from month to month. In a random sample of 310 college students, 217 carried a balance each month. Find a 95% Confidence interval for the proportion that carry a balance. Example 3. Determining Sample Size Suppose you want to estimate the proportion of doctors that have participated in doctor-assisted suicide to within .01 with 90% confidence. How many should you have in your sample?...
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