1. Chapter 9.2: Sample Proportion Mr. Lynch AP Statistics

2. Sample Proportions In what year did Christopher Columbus “discover” America? What is our classes p-hat? 210 of the 501 sampled in a Gallup Poll knew this.

3. Rules of Thumb RULE OF THUMB 1: You can only use the standard deviation formula of the population is large enough. Specifically N  10n RULE OF THUMB 2: You can only use A NORMAL APPROXIMATION to the propoprtion sampling distribution with values of n and p if np  10 AND nq  10

4. The Normal Approximation When n is LARGE, the Sampling Distribution of is approximately normal EXAMPLE 9.7: APPLYING TO COLLEGE SRS OF n = 1500; p =.35 Check Rules of Thumb P(the random sample will produce a percentage within 2% of the actual population proportion of 35%)

5. The Normal Approximation Draw it! Standardize the p-hat values Re-draw with the new z-scores Calculate Area with table or normalcdf

6. SURVEY UNDERCOVERAGE EXAMPLE 9.8 SURVEY UNDERCOVERAGE? 11% US adults are black A recent national sample of 1500 adults had only a 9.2% black representation Should we suspect racial discrimination or some sort of under- coverage?

7. SURVEY UNDERCOVERAGE Rules of Thumb Draw it! Standardize the p-hat value Re-draw with the new z-score Calculate Area with table or normalcdf