# 9.2E: Outcomes and the Type I and Type II Errors (Exercises)

- Page ID
- 6965

Exercise 9.3.5

The mean price of mid-sized cars in a region is $32,000. A test is conducted to see if the claim is true. State the Type I and Type II errors in complete sentences.

**Answer**-
**Type I**: The mean price of mid-sized cars is $32,000, but we conclude that it is not $32,000.**Type II**: The mean price of mid-sized cars is not $32,000, but we conclude that it is $32,000.

Exercise 9.3.6

A sleeping bag is tested to withstand temperatures of –15 °F. You think the bag cannot stand temperatures that low. State the Type I and Type II errors in complete sentences.

Exercise 9.3.7

For Exercise 9.12, what are \(\alpha\) and \(\beta\) in words?

**Answer:**-
\(\alpha =\) the probability that you think the bag cannot withstand -15 degrees F, when in fact it can

\(\beta =\) the probability that you think the bag can withstand -15 degrees F, when in fact it cannot

Exercise 9.3.8

In words, describe \(1 - \beta\) For Exercise 9.12.

Exercise 9.3.9

A group of doctors is deciding whether or not to perform an operation. Suppose the null hypothesis, \(H_{0}\), is: the surgical procedure will go well. State the Type I and Type II errors in complete sentences.

**Answer:**-
**Type I**: The procedure will go well, but the doctors think it will not.**Type II:**The procedure will not go well, but the doctors think it will.

Exercise 9.3.10

A group of doctors is deciding whether or not to perform an operation. Suppose the null hypothesis, \(H_{0}\), is: the surgical procedure will go well. Which is the error with the greater consequence?

Exercise 9.3.11

The power of a test is 0.981. What is the probability of a Type II error?

**Answer:**-
0.019

Exercise 9.3.12

A group of divers is exploring an old sunken ship. Suppose the null hypothesis, \(H_{0}\), is: the sunken ship does not contain buried treasure. State the Type I and Type II errors in complete sentences.

Exercise 9.3.13

A microbiologist is testing a water sample for E-coli. Suppose the null hypothesis, \(H_{0}\), is: the sample does not contain E-coli. The probability that the sample does not contain E-coli, but the microbiologist thinks it does is 0.012. The probability that the sample does contain E-coli, but the microbiologist thinks it does not is 0.002. What is the power of this test?

**Answer**-
0.998

Exercise 9.3.14

A microbiologist is testing a water sample for E-coli. Suppose the null hypothesis, \(H_{0}\), is: the sample contains E-coli. Which is the error with the greater consequence?