Free Printable STAT Confidence Intervals Mean Pop SD Known

1.

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)

1.799

b)

1.798

c)

1.803

2.

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

3.

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 critical value.

a)

0.90

b)

1.155

c)

1.645

d)

±1.645

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.

Find the Margin of Error to two decimal places.

a)

1.90

b)

1.89

c)

1.899

d)

1.99

5.

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. 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)

6.

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

7.

A population has a standard deviation of σ = 17.3. How large of a sample must be drawn so that a 95% confidence interval for µ will have a Margin of Error equal to 1.4?

a)

586.6

b)

587

c)

586

d)

585

8.

Find the Critical Value for an 86% Confidence Level.

a)

-1.48

b)

1.48

c)

1.282

d)

-1.47

9.

True or False:

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

a)

True

b)

False

10.

True or False:

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

a)

True

b)

False

STAT Confidence Intervals Mean Pop SD Known

Total questions: 10

Worksheet time: 26mins

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