1. Hypothesis Tests for Proportions

2. The Random Variable Recall –Normal distribution –Mean  = p –Standard Deviation =

3. Hypothesis Testing for Proportions H 0 : p = p 0 H A : p > p 0 Test is Reject H 0 (Accept H A ) if z > z  The test statistic, z, is:

4. EXAMPLE Taste test between Coke and Pepsi 1000 cola drinkers tested 540 say they prefer Coke Can we conclude that more than 50% of cola drinkers favor Coke over Pepsi? Note:

5. The Hypothesis Test p = true proportion of all cola drinkers who favor Coke H 0 : p =.5 H A : p >.5  =.05 Reject H 0 if z > z.05 = 1.645

6. 1000 Count the number of alphanumeric observations =COUNTA(A2:A1001) 540 Count the number of “COKE” observations =COUNTIF(A2:A1001, “COKE”).54 x/n =C6/C5 2.52982 =(C9-.5)/sqrt((.5*.5)/C5) 0.00571 =1-NORMSDIST(C11)

7. Review The point estimate for p is: The test statistic, z, is: Use of Excel (COUNTA, COUNTIF Functions)