Chapter 10: Confidence Intervals - PowerPoint PPT Presentation

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Chapter 10: Confidence Intervals. Section 2: Estimating a Population Proportion. Margin of Error. To calculate our margin of error in this case, we will use:. CI for Population Proportion (when p is known ).

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Chapter 10: Confidence Intervals

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Chapter 10: Confidence Intervals

Section 2: Estimating a Population Proportion

Margin of Error

• To calculate our margin of error in this case, we will use:

CI for Population Proportion(when pis known)

• Choose a SRS of size n from a population having unknown proportion p of successes. An approximate level C confidence interval for pis:

PRACTICE IT!

• A May 2000 Gallup Poll found that 38% of a random sample of 1012 adults said that they believe in ghosts. Find a 95% confidence interval for the true proportion of adults who believe in ghost.

• We are 95% confident that the true proportion of adults who believe in ghosts is between 35% and 41%.

Determining Sample Size

• If we wanted to determine an appropriate sample size for a desired margin of error we would use:

PRACTICE IT!

• Another Gallop Poll is taken in order to measure the proportion of adults who approve of attempts to clone humans. What sample size is necessary to be within + 0.04 of the true proportion of adults who approve of attempts to clone humans with a 95% Confidence Interval?