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Confidence Intervals (C.I.)

Confidence Intervals (C.I.). Determine the percent of samples that should contain the actual probability. Conditions and Assumptions. Independent trials Random sample Sample less than 10% of population Success/Failure ( np & nq => 10). Pg 1.2 conditions met?.

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Confidence Intervals (C.I.)

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  1. Confidence Intervals (C.I.) Determine the percent of samples that should contain the actual probability.

  2. Conditions and Assumptions Independent trials Random sample Sample less than 10% of population Success/Failure (np & nq => 10) Pg 1.2 conditions met?

  3. The most common critical values are: 99.9% - for medical content 99% 95% - for most other content 90% 80% Critical Value What percent of confidence do you want to claim when you are done?

  4. Z* 99% : 2.575 z’s 98% : 2.326 z’s 95% : 1.960 z’s 90% : 1.645 z’s 80% : 1.282 z’s The number of standard deviations that give you a particular percent of the total model. Pg 1.3 critical value?

  5. The Mean and Standard Error Called the Standard Error instead of the standard deviation because we are estimating the population parameter. Pg 1.4 p-hat? Pg 1.5 SE(p-hat)?

  6. Margin of Error (ME) ME = z* x SE Half the width of the C.I. or the center of bob to the z*. Pg 1.6 ME?

  7. The Confidence Interval An area of bob, centered at the center p and has length of 2 ME Pg 1.7 90% CI lower CI upper CI

  8. The meaning of the C.I. in context We are ____% confident that the actual proportion is between lower end and upper end. C.I.’s constructed in this manner will contain the true proportion in _____ % of all samples.

  9. Determine the Sample Size If you know what you want your ME to be, you can determine how big a sample size you need – use algebra! Pg 1.8 Sample size for 95% CI

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