AP Statistics : How to do tests of significance for a difference between two means

Study concepts, example questions & explanations for AP Statistics

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Example Questions

Example Question #4 : Ap Statistics

Suppose you conduct a paired -test to assess whether two group means significantly differ and find a -score of 1.645. At what alpha level would this cause you to reject the null?

Possible Answers:

Correct answer:

Explanation:

The critical value for a -test with alpha set to 0.10 is 1.645.

Example Question #5 : Ap Statistics

Bob wants to statistically determine if the mean height of middle school boys is greater than the mean height of middle school girls. He wants to use a significance level of  What must be true for him to reject . is known.

Possible Answers:

Correct answer:

Explanation:

Step 1: We need to use a 2-sample z test because there are 2 samples, boys and girls. The population standard deviation, , is known, so we can assume a standard distribution for each sample.

Step 2: This is a one-sided z test because the questions asks if the mean height of boys is greater than the mean height of girls.

Step 3: significance level, or alpha, is . This means we need a p-value less than  in order to reject the null hypothesis . A z-score greater than would ensure a p-value less than .

 

Curve p value

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