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Stat Tutor

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2:02

Incorrect. Using the “plus four” confidence interval to estimate *p*_{1} - p_{2} improves the accuracy of the level of confidence when the sample sizes are not very large.

Correct. Using the “plus four” confidence interval to estimate *p*_{1} - p_{2} improves the accuracy of the level of confidence when the sample sizes are not very large.

Incorrect. Try again.

2

2:47

Incorrect. Both sample sizes need to be at least 5 in order to estimate *p*_{1} - *p*_{2} with a "plus four" confidence interval.

Correct. Both sample sizes need to be at least 5 in order to estimate *p*_{1} - *p*_{2} with a "plus four" confidence interval.

Incorrect. Try again.

2

3:45

Incorrect. The two treatments were: duct tape and freezing; the explanatory variable is type of wart removal (or whether duct tape or feezing was used to get rid of a wart.)

Correct. The two treatments were: duct tape and freezing; the explanatory variable is type of wart removal (or whether duct tape or feezing was used to get rid of a wart.)

Incorrect. Try again.

2

Incorrect. The outcome measured on each patient was whether their wart was removed. This is the response variable.

Correct. The outcome measured on each patient was whether their wart was removed. This is the response variable.

Incorrect. Try again.

2

Incorrect. We use a two-sample proportion procedure to analyze these data because both explanatory and response variables are categorical and both have only two categories.

Correct. We use a two-sample proportion procedure to analyze these data because both explanatory and response variables are categorical and both have only two categories.

Incorrect. Try again.

2

4:24

Incorrect. The sample sizes are 22 and 26 which are too small for a large sample confidence interval for *p*_{1 }- p_{2}.

Correct. The sample sizes are 22 and 26 which are too small for a large sample confidence interval for *p*_{1 }- p_{2}.

Incorrect. Try again.

2

5:17

Incorrect. The sample sizes are 26 and 25; since both are bigger than 5, they are big enough.

Correct. The sample sizes are 26 and 25; since both are bigger than 5, they are big enough.

Incorrect. Try again.

2

6:09

Incorrect. The value of 0.233 is the margin of error.

Correct. The value of 0.233 is the margin of error.

Incorrect. Try again.

2

6:43

Incorrect. *p*_{1} - p_{2} is a parameter and thus must be stated as such. It is the difference between two population proportions. *p*_{1 }= the proportion of all patients with warts who get rid of them using duct tape and *p*_{2 }= the proportion of all patients with warts who get rid of them using freezing.

Correct. *p*_{1} - p_{2} is a parameter and thus must be stated as such. It is the difference between two population proportions. *p*_{1 }= the proportion of all patients with warts who get rid of them using duct tape and *p*_{2 }= the proportion of all patients with warts who get rid of them using freezing.

Incorrect. Try again.

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