Inference for Population Proportions

  Inference means what you make out of data  Statistics is the practice of measuring Data  Significance! The less the p-value, the more significant!  The larger the difference from the expected mean or the other sample, the Lower the p-value. Review!

  P-value is calculated by how many standard deviations your value is from the expected value  The p-value IS the proportion of observations that fall above or below your test statistic  The p-value MEANS the probability that your data happened randomly  Lower p-value, more significance because the probability of the event occurring by chance is so slim, there must be another contributing factor P-Value!

 Test Statistic:Confidence Interval: One Sample: Find significance of our data compared to what’s expected Estimates a range in which we think the population value lies Two Samples: Find significance of the difference between our samples Estimate a range in which we think the difference of the populations lies Purpose!

 Likelihood

  Many Studies are about proportions, as well as means  Examples of Populations Proportions:  Risky behavior and AIDS – Find percentage of adults who put themselves at risk  Preschool making a difference – comparing the success rate between people who had and who had no preschool Proportion Studies

 Proportion Inference

 Example: Dorm Food

 Example: Tuition

 Inference Conditions

 The Z Procedures

  The 1995 Harvard School of Public Health College Alcohol Study examined alcohol use, including “binge drinking”  Binge Drinking was defined as consuming five or more dinks on at least one occasion (four for women)  Binge Drinkers experience a higher percentage of alcohol related problems, such as disciplinary problems, violence, irresponsible sexual activity, personal injury, and bad grades Ex 12.6: Binge Drinking

 Step 1: Hypotheses

 Step 2: Conditions

 Step 3: Procedure

 Step 4: Interpret

 Further Discussion

  Press [STAT], scroll to “TESTS”.  Select “1PropZ-Test” for a significance test  Select “1PropZint” for a confidence interval Calculator Shortcuts:

  Page 694, 12.6 – 12.9 Practice