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Points and Interval Estimation

Total questions: 12

Worksheet time: 20mins

Name
Class
Date
1.
The confidence level of an interval estimate of a parameter is the probability that the interval estimate will contain the parameter.
a)
True
b)
False
2.
A research company wants to estimate the proportion of people who like oatmeal.  They want the confidence level to be 95%.  The company gets 325 people to sign up for the survey, but on the day that the survey is issued, only 250 people show up and take the survey.  What happens to the confidence interval?
a)
It gets larger
b)
It gets smaller
c)
It stays the same
d)
Too little information given
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)

1.799

b)

1.798

c)

1.803

4.

A large sample has mean of 7.1 and Standard Error of 2.3.


Construct a 90% Confidence Interval for the population mean µ (to two decimal places).

a)

(3.32, 10.88)

b)

(3.8, 7.1)

c)

(3.3, 10.9)

d)

(3.3165, 10.8835)

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.


What is the point estimate?

a)

75

b)

105.2

c)

10

d)

0.90

6.

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)

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.

True or False:


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

a)

True

b)

False

9.

True or False:


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

a)

True

b)

False

10.
What can you do to reduce the margin of error? 
a)
increase the confidence level
b)
decrease the confidence level
c)
increase sample size
d)
decrease sample size
11.
When interpreting the confidence interval, make sure that you are describing the 
a)
statistic
b)
parameter
12.
Construct a 90% confidence interval of a random sample size of 19 cows with a mean of 155.526 and a standard deviation of 19.993. 
a)
(146.54, 164.52)
b)
(147.57, 163.48)
c)
(147.59, 163.46)
d)
(143.69, 167.36)