# Chapter 1. Planning Studies Part 2: Type I and Type II Errors of a Statistical Test*

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Stat Tutor
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1:19

### Question 1.1

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Incorrect. Errors are possible in any decision making process.
Correct. Errors are possible in any decision making process.
Incorrect. Try again.
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2:19

### Question 1.2

What errors could a jury make in deciding whether a defendant is innocent or guilty? Check all that apply.

3hMJDRP6OS+3EJIba. Deciding a defendant is guilty when he is guilty.

wg8JNehuALfILP6Sb. Deciding a defendant is guilty when he is innocent.

wg8JNehuALfILP6Sc. Deciding a defendant is not guilty when he is guilty.

3hMJDRP6OS+3EJIbd. Deciding a defendant is not guilty when he is innocent.

Incorrect. Deciding a defendant is guilty when he is innocent or deciding he is not guilty when he is guilty are both errors that could be made by the jury.
Correct. Deciding a defendant is guilty when he is innocent or deciding he is not guilty when he is guilty are both errors that could be made by the jury.
Incorrect. Try again.
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4:26

### Question 1.3

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Incorrect. In the United States, the null hypothesis is that the defendant is innocent.
Correct. In the United States, the null hypothesis is that the defendant is innocent.
Incorrect. Try again.
2

5:16

### Question 1.4

Which of the following are correct decisions? Check all that apply.

wg8JNehuALfILP6Sa. Deciding a defendant is guilty when he is guilty.

3hMJDRP6OS+3EJIbb. Deciding a defendant is guilty when he is innocent.

3hMJDRP6OS+3EJIbc. Deciding a defendant is not guilty when he is guilty.

wg8JNehuALfILP6Sd. Deciding a defendant is not guilty when he is innocent.

Incorrect. Deciding a defendant is guilty when he is guilty or deciding he is not guilty when he is innocent are both correct decisions.
Correct. Deciding a defendant is guilty when he is guilty or deciding he is not guilty when he is innocent are both correct decisions.
Incorrect. Try again.
2

6:24

### Question 1.5

yoVRWHLFR8oCQgMyMBwij+RK0MV5ZsDwa64Wrf6Qf04I3d9ORxm7/PW3V91ixObAHkBDQOGwyc8K5qkrEZDk+xDkdc4oxhmy/c8yLKxuU95hiPHnRXhDkJ58rZiynogw8m3VRVYFDm1oML4sN21bdFe2zSu6VmSxHHEySKxD30B4nPkJ6vVsBtLe6B4RHm3iz1Yf1T15dZzbDjNR1IC4q6DyByBW0IhNaKGlKg==
Incorrect. A type I error occurs when a correct null hypothesis is rejected.
Correct. A type I error occurs when a correct null hypothesis is rejected.
Incorrect. Try again.
2

8:04

### Question 1.6

Incorrect. The jury declared Bishop guilty when she was really innocent. Thus, she was hung when she should have been set free.
Correct. The jury declared Bishop guilty when she was really innocent. Thus, she was hung when she should have been set free.
Incorrect. Try again.
2

12:30

### Question 1.7

Incorrect. A type I error is made by rejecting H0 when it is correct. In this case, you would reject H0 and conclude that the brownies are done when H0 is correct and the brownies are NOT done.
Correct. A type I error is made by rejecting H0 when it is correct. In this case, you would reject H0 and conclude that the brownies are done when H0 is correct and the brownies are NOT done.
Incorrect. Try again.
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### Question 1.8

Incorrect. A type II error is made by failing to reject H0 when it is incorrect. In this case, you would stay with H0 and conclude that the brownies are NOT done when H0 is incorrect and the brownies really are done.
Correct. A type II error is made by failing to reject H0 when it is incorrect. In this case, you would stay with H0 and conclude that the brownies are NOT done when H0 is incorrect and the brownies really are done.
Incorrect. Try again.
2

### Question 1.9

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Incorrect. Deciding that the brownies are done when they are not results in underdone, gooey brownies.
Correct. Deciding that the brownies are done when they are not results in underdone, gooey brownies.
Incorrect. Try again.
2

13:32

### Question 1.10

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Incorrect. A type I error is only possible if you reject H0.
Correct. A type I error is only possible if you reject H0.
Incorrect. Try again.
2

### Question 1.11

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Incorrect. A type I error is only possible if you reject H0.
Correct. A type I error is only possible if you reject H0.
Incorrect. Try again.
2

### Question 1.12

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Incorrect. A type I error can only occur when you reject H0 and a type II error can only occur when you fail to reject H0. Since you cannot both reject H0 and fail to reject H0 at the same time, you cannot make a type I error and a type II error at the same time.
Correct. A type I error can only occur when you reject H0 and a type II error can only occur when you fail to reject H0. Since you cannot both reject H0 and fail to reject H0 at the same time, you cannot make a type I error and a type II error at the same time.
Incorrect. Try again.
2

15:30

### Question 1.13

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Incorrect. α is the symbol for level of significance and is the probability of making a type I error.
Correct. α is the symbol for level of significance and is the probability of making a type I error.
Incorrect. Try again.
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### Question 1.14

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Incorrect. Power is defined as the probability of rejecting the null hypothesis when it is wrong.
Correct. Power is defined as the probability of rejecting the null hypothesis when it is wrong.
Incorrect. Try again.
2

17:34

### Question 1.15

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Incorrect. For fixed sample size, increasing α decreases the probability of making a type II error.
Correct. For fixed sample size, increasing α decreases the probability of making a type II error.
Incorrect. Try again.
2

### Question 1.16

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Incorrect. For fixed α, increasing sample size increases power.
Correct. For fixed α, increasing sample size increases power.
Incorrect. Try again.
2

### Question 1.17

Which of the following increases power? Select all that apply.

wg8JNehuALfILP6Sa. Increasing α

3hMJDRP6OS+3EJIbb. Decreasing α

wg8JNehuALfILP6Sc. Increasing sample size

3hMJDRP6OS+3EJIbd. Decreasing sample size

Incorrect. Increasing either α or sample size increases power.
Correct. Increasing either α or sample size increases power.
Incorrect. Try again.
2

17:58

### Question 1.18

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Incorrect. α is the symbol for probability of making a type I error, not just making a type I error.
Correct. α is the symbol for probability of making a type I error, not just making a type I error.
Incorrect. Try again.
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