Question 1

i. The 95 percent conﬁdence interval states that 95 percent of the sample means of a speciﬁed
Sample size selected from a population will lie within plus and minus 1.96 standard deviations of the
Hypothesized population mean.
ii. A distribution of sample means is normally distributed with a mean equal to the population mean
And a standard deviation equal to the standard error of the mean.
iii. A sample mean is the best point estimate of a population mean.

Accepted Answer

(i), (ii), and (iii) are all correct statements.

Question 2

The z-value associated with a 90% level of conﬁdence is:

Accepted Answer

1.645

Question 3

The z-value associated with an 80% level of conﬁdence is:

Accepted Answer

1.28

Question 4

A random sample of 85 group leaders, supervisors, and similar personnel revealed that on the
Average a person spent 6.5 years on the job before being promoted. The standard deviation of the
Population was 1.7 years. Find the 95% conﬁdence interval for the population mean.

Accepted Answer

6.14 and 6.86

Question 5

Recently, a university surveyed recent graduates of the English Department for their starting
Salaries. Four hundred graduates returned the survey. The average salary was $25,000. The
Population standard deviation is known to be $2,500.
Interpret the results of the 95% conﬁdence interval.

Accepted Answer

The likelihood that any conﬁdence interval based on a sample of 400 graduates will

Question 6

Recently, a university surveyed recent graduates of the English Department for their starting
Salaries. Four hundred graduates returned the survey. The average salary was $55,000 with a
Standard deviation of $2,500.
What is the best point estimate of the population mean?

Accepted Answer

$55,000

Question 7

A sample mean is the best point estimate of the

Accepted Answer

population mean.

Question 8

Dottie Kleman is the "Cookie Lady." She bakes and sells cookies at 50 different locations. Ms.
Kleman is concerned about absenteeism among her workers. The information below reports the
Number of days absent for a sample of 10 workers during the last two-week pay period. 
The sample mean is calculated to be 1.8 and sample standard deviation is 1.1353. Develop a 95%
Conﬁdence interval for the population mean. Assume that the population distribution is normal. Is it
Reasonable to conclude that the typical worker misses 1 day during a pay period?

Accepted Answer

[0.99, 2.61] It is reasonable to conclude that the mean number of days of work missed is 1

Question 9

Mileage tests were conducted on a randomly selected sample of 100 newly developed automobile
Tires. The average tread life was found to be 80,000 kilometres with a standard deviation of 5,600
Kilometres. What is the best estimate of the average tread life in miles for the entire population of
These tires?

Accepted Answer

80,000

Question 10

A 95% conﬁdence interval infers that the population mean is

Accepted Answer

within ± 1.96 standard errors of the sample mean.

Question 11

A sample of 25 is selected from a known population of 100 elements. What is the ﬁnite population
Correction factor?

Accepted Answer

0.87

Question 12

The z-value associated with a 96% level of conﬁdence is:

Accepted Answer

2.05

Question 13

Recently, a university surveyed recent graduates of the English Department for their starting
Salaries. One hundred graduates returned the survey. The average salary was $35,000 with a
Standard deviation of $2,000.
What is the best point estimate of the population mean?

Accepted Answer

$35,000

Question 14

A sample of 50 is selected from a known population of 250 elements. The population standard
Deviation is 15. What is the standard error of the sample means using the ﬁnite population
Correction factor?

Accepted Answer

1.90

Question 15

Dottie Kleman is the "Cookie Lady." She bakes and sells cookies at 50 different locations. Ms.
Kleman is concerned about absenteeism among her workers. The information below reports the
Number of days absent for a sample of 10 workers during the last two-week pay period. 
The sample mean is calculated to be 1.8 and sample standard deviation is 1.1353. Develop a 95%
Conﬁdence interval for the population mean. Assume that the population distribution is normal. Is it
Reasonable to conclude that the typical worker does not miss any days during a pay period?

Accepted Answer

[0.99, 2.61] It is unreasonable to conclude that the mean number of days of work missed is

Question 16

Which of the following would be used as a point estimate for the population mean (µ)?

Accepted Answer

The answer of Which of the following would be used...

Question 17

A sample standard deviation is the best point estimate of the

Accepted Answer

population standard deviation.

Question 18

When a conﬁdence interval for a population mean is constructed from sample data,

Accepted Answer

we can conclude, with a stated level of conﬁdence, that the population mean is in the

Question 19

The z-value associated with a 94% level of conﬁdence is:

Accepted Answer

1.88

Question 20

A conﬁdence interval for a population mean

Accepted Answer

estimates a likely interval for a population mean.

Quiz 8: Sampling Methods and the Central Umit Theorem

The z-value associated with a 90% level of conﬁdence is:

The z-value associated with an 80% level of conﬁdence is:

A random sample of 85 group leaders, supervisors, and similar personnel revealed that on the Average a person spent 6.5 years on the job before being promoted. The standard deviation of the Population was 1.7 years. Find the 95% conﬁdence interval for the population mean.

Recently, a university surveyed recent graduates of the English Department for their starting Salaries. Four hundred graduates returned the survey. The average salary was $25,000. The Population standard deviation is known to be $2,500. Interpret the results of the 95% conﬁdence interval.

Recently, a university surveyed recent graduates of the English Department for their starting Salaries. Four hundred graduates returned the survey. The average salary was $55,000 with a Standard deviation of $2,500. What is the best point estimate of the population mean?

A sample mean is the best point estimate of the

A 95% conﬁdence interval infers that the population mean is

A sample of 25 is selected from a known population of 100 elements. What is the ﬁnite population Correction factor?

The z-value associated with a 96% level of conﬁdence is:

Recently, a university surveyed recent graduates of the English Department for their starting Salaries. One hundred graduates returned the survey. The average salary was $35,000 with a Standard deviation of $2,000. What is the best point estimate of the population mean?

A sample of 50 is selected from a known population of 250 elements. The population standard Deviation is 15. What is the standard error of the sample means using the ﬁnite population Correction factor?

Which of the following would be used as a point estimate for the population mean (µ) ?

A sample standard deviation is the best point estimate of the

When a conﬁdence interval for a population mean is constructed from sample data,

The z-value associated with a 94% level of conﬁdence is:

A conﬁdence interval for a population mean