AP Statistics : How to do large sample tests of significance for differences between two proportions

Study concepts, example questions & explanations for AP Statistics

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Example Questions

Example Question #1 : Significance

We are comparing the Democratic percentage of Detroit to the Democratic percentage of Dallas. 

In Detroit, we sampled 300 people and 208 were Democrats (.693)

In Dallas, we sampled 350 people and 265 were Democrats (.757)

What is the p-value for the .064 difference?

(Assume a 2-tailed test.)

Possible Answers:






Correct answer:



Overall percentage =

.0344 is for one tail, so .0688 is for both tails.

(Percentages are different at the .9312 level.)

Example Question #2 : Inference



Possible Answers:




Correct answer:




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