Quiz about Confidence Intervals

Question 1

Which of the following is the definition of a "point estimate?"

Accepted Answer

The midpoint of the confidence interval

Answer

The sample size

Answer

The population

Answer

The standard deviation

Question 2

The amount added and subtracted to the statistic.

Accepted Answer

Margin of error

Answer

Statistic

Answer

Population

Answer

Point estimator

Question 3

What is the point estimator for the interval (5 , 13)?

Accepted Answer

9

Answer

10

Answer

11

Answer

8

Question 4

What is the margin of error for the interval (6.8, 12.9)?

Accepted Answer

3.05

Answer

9.85

Answer

5.83

Answer

8.41

Question 5

An IQ test was given to a simple random sample of 75 students at a certain college. The sample mean score was 105.2. Scores on this test are known to have a standard deviation of 10. It is desired to construct a 90% confidence interval for the mean IQ scores of the students at the college.

Find the point estimate.

Accepted Answer

105.2

Answer

10

Answer

.90

Answer

75

Question 6

An IQ test was given to a simple random sample of 75 students at a certain college. The sample mean score was 105.2. Scores on this test are known to have a standard deviation of 10. It is desired to construct a 90% confidence interval for the mean IQ scores of the students at the college.

Find the point estimate.

Find the Critical Value for the mean.

Accepted Answer

1.67

Answer

1.28

Answer

-1.67

Answer

-1.28

Question 7

The lifetime of a certain type of batter is known to be normally distributed with a standard deviation of 20 hours. A sample of 50 batteries had a mean lifetime of 120.1 hours. Construct a 99% confidence interval for the mean lifetime of this type of battery.

Accepted Answer

(112.52, 127.68)

Answer

(111.2, 128.9)

Answer

(114.53, 131.23)

Answer

(118.43, 122.43)

Question 8

Find the Critical Value for an 86% Confidence Level for a proportion.

Accepted Answer

1.48

Answer

-1.48

Answer

1.96

Answer

-1.96

Question 9

True or False:

The more confident you want to be, the smaller your confidence interval will be.

Accepted Answer

False

Answer

True

Question 10

In a survey of 104 students, it was found that 79 went to the homecoming game this year.

Calculate a 99% confidence interval for p.

Accepted Answer

(.65, .87)

Answer

(.59, .79)

Answer

(.62, .85)

Answer

(.60, .90)

Question 11

For a sample, the 95% confidence interval is (0.202, 0.482).

What is the margin of error of this sample?

Accepted Answer

.14

Answer

.21

Answer

.344

Answer

.342

Question 12

Which of the following does NOT have an affect on the width of a confidence interval?

Accepted Answer

Sample mean

Answer

Standard deviation

Answer

Sample size

Answer

Critical value

Question 13

Which of the following changes to a study would result in a narrower confidence interval?

Accepted Answer

decreasing the confidence level, increasing the sample size

Answer

increasing the confidence level, decreasing the sample size

Answer

increasing the confidence level, increasing the sample size

Answer

decreasing the confidence level, decreasing the sample size

Confidence Intervals

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