Free Printable Confidence Intervals

1.

True or False:

The larger your confidence interval is, the more sure (higher confidence level) you can be.

a)

True

b)

False

2.

True or False:

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

a)

True

b)

False

3.

A sample size of n = 64 is drawn from a population whose standard deviation is σ = 5.6.

Find the margin of error for a 99% confidence interval for µ.

a)

1.672

b)

1.798

c)

1.803

d)

1.594

4.

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.

What is the point estimate?

a)

75

b)

105.2

c)

10

d)

0.90

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 Margin of Error to two decimal places.

a)

1.751

b)

1.634

c)

1.899

d)

1.909

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.

Calculate the confidence interval.

a)

101 to 104

b)

100 to 105

c)

99.5 to 105

d)

98.7 to 106

7.

If the 95% Confidence Interval for a population mean is (114.56, 125.54), then is it likely that the true population mean µ is greater than 130?

a)

Yes

b)

No

c)

Not enough information

d)

I have no idea what you're asking of me

8.

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

a)

10

b)

9.5

c)

9

d)

-5

9.

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

a)

9.85

b)

3.05

c)

3.50

d)

6.8

10.

A 90% confidence interval for the average salary of all CEOs in the electronics industry was constructed using the results of a random survey of 45 CEOs. The interval was ($139,048, $154,144). Give a practical interpretation of the interval.

a)

90% of the sampled CEOs have salaries that fell in the interval $139,048 to $154,144

b)

We are 90% confident that the mean salary of all CEOs in the electronics industry falls in the interval $139,048 to $154,144.

c)

90% of all CEOs in the electronics industry have salaries that fall between $139,048 to $154,144

d)

We are 90% confident that the mean salary of the sampled CEOs falls in the interval $139,048 to $154,144.

11.

The lifetime of a certain type of battery 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. It is desired to construct a 99% confidence interval for the mean lifetime of this type of battery.

What is the Confidence Interval to one decimal place?

a)

(114.5, 125.6)

b)

(112.8, 127.4)

c)

(112.82, 127.38)

d)

(114.56, 125.64)

Confidence Intervals

Total questions: 11

Worksheet time: 21mins

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