Assignment # 0192LA3

CP Statistics – Ch 8 & 10 Confidence Interval Review 1. Which of the following is the critical value for calculating a 94% confidence interval for a

population proportion?

a. 1.555

b. 1.645

c. 1.881

d. 1.960

e. 2.576

2. You want to compute a 90% confidence interval for the mean difference in height for mothers and

their adult daughters using a random sample of 30 mothers who have an adult daughter. What

critical value should you use for this interval?

a. 1.645

b. 1.671

c. 1.697

d. 1.699

e. 1.761

3. To compute a 95% confidence interval for the mean GPA of all athletes in Ventura County, you take a random sample of 105 athletes. Select the degrees of freedom from the choices below.

a. 100

b. 104

c. 105

d. 106

e. 110

4. Explain the difference between the Normal Conditions: 1) Large Counts and 2) Large Sample.

5. Thirty-five people from a random sample of 125 workers from Company A admitted to using sick leave when they weren’t really ill. Seventeen employees from a random sample of 68 workers from

Company B admitted that they had used sick leave when they weren’t ill. Which of the following is

a 95% confidence interval for the difference in the proportions of workers at the two companies who

would admit to using sick leave when they weren’t ill?

6. In which of the following situations below has the Normal Condition for Large Sample been met? Select all that apply.

a. A 95% confidence interval based on n=10 randomly selected observations, with a symmetric graph and only one outlier.

b. A 99% confidence interval from an SRS of 20 observations with a slight skew to the left and no outliers.

c. A 90% confidence interval based on a random sample of 77 individuals with one outlier.

d. A 90% confidence interval based on n=12 randomly selected observations, nothing known about the graph.

e. A 95% confidence interval from an SRS of 32 observations, nothing known about the graph.

f. A 99% confidence interval based on a random sample of size 58, nothing known about the graph.

7. Do high school seniors with part-time jobs spend less time doing homework per week, on average,

than seniors without part-time jobs? For a random sample of 45 seniors with part-time jobs, the

mean amount of homework time is 4.2 hours with a standard deviation of 3.8 hours. For a random

sample of 45 seniors without part time jobs, the mean amount of homework time is 5.8 hours with a

standard deviation of 4.9 hours. Assuming the conditions are met, which of the following is the

correct standard error for a 95% confidence interval for a difference in the population means?

8. A recent study asked U.S. adults to name 10 historic events that occurred in their lifetime that have

had the greatest impact on the country. The most frequently chosen answer was the September 11,

2001, terrorist attacks, which was included by 76% of the 2,025 randomly selected U.S. adults.

Construct and interpret a 95% confidence interval for the true proportion of all U.S. adults who

would include the 9/11 attacks on their list of 10 historic events. Clearly list out all of the steps in

PANIC. (Chapter 8)

9. A milk processor monitors the number of bacteria per milliliter in raw milk received at the factory. A random sample of 10 one-milliliter specimens of milk supplied by one producer gives the

following data:

5370 4890 5100 4500 5260 5150 4900 4760 4700 4870

Construct and interpret a 90% confidence interval for the population mean μ. You are informed that the assumptions in PANIC have been met. (Chapter 10)

10. Ashtyn and Olivia wanted to know if generic chocolate chip cookies have as many chocolate

chips as name-brand chocolate chip cookies, on average. To investigate, they randomly selected

10 bags of Chips Ahoy!® cookies and 10 bags of Great Value cookies and randomly selected 1

cookie from each bag. Then they carefully broke apart each cookie and counted the number of

chocolate chips in each. Here are their results:

Chips Ahoy: 17 19 21 16 17 18 20 21 17 18

Great Value: 22 20 14 17 21 22 15 19 26 18

Let mean1 = the true mean number of chocolate chips for all Chips Ahoy! chocolate chip cookies

and mean2 = the true mean number of chocolate chips for all Great Value chocolate chip cookies.

Check if the conditions for calculating a confidence interval for m1 = m2 are met. (Chapter 10)