Module 02 Homework: Inferential Statistics and Analytics

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Name: ______________________________________

Module 2 Homework Assignment

1.) 459 randomly selected light bulbs were tested in a laboratory, 291 lasted more than 500 hours. Find a point estimate of the true proportion of all light bulbs that last more than 500 hours.

Solution:

Instructor Comments:

2.) Find the critical value for zα/2 that corresponds to a degree of confidence of 98%.

Solution:

Instructor Comments:

3.) Find the critical value for tα/2 corresponding to n = 12 and 95% confidence level.

Solution:

Instructor Comments:

4.) Use the confidence level and sample data to find the margin of error E.

College students’ annual earnings:

99% confidence, n = 74, = $3967, s = $874

Solution:

Instructor Comments:

5.) Construct the confidence interval for question 4 above.

Solution:

Instructor Comments:

6.) Write a statement that correctly interprets the confidence interval found in question 5.

Solution:

Instructor Comments:

7.)

Find the critical value corresponding to a sample size of 19 and a confidence level of 99% if the test is two-tailed.

Solution:

Instructor Comments:

8.)

Find the critical value corresponding to a sample size of 19 and a confidence level of 99% if the test is two-tailed.

Solution:

Instructor Comments:

9.)

The values listed below are the waiting times (in minutes) of customers at the Bank of Providence, where customers enter any one of three different lines that have formed at three teller windows. Construct a 95% confidence interval for the population standard deviation and write a statement that correctly interprets the results.

4.2 5.4 5.8 6.2 6.7 7.7 8.5 9.3 10.0

Solution:

Instructor Comments:

10.) You want to estimate for the population of waiting times at a fast-food restaurant’s drive-up windows, and you want to be 95% confident that the sample standard deviation is within 20% of . Find the minimum sample size needed. Is this sample size practical?

Solution:

Instructor Comments:

2

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c

s

x

2

L

c

Name: _

_____________________________________

Module 2 Homework Assignment

1.)

459 randomly selected light bulbs were tested in a laboratory, 291 lasted more than 500 hours.

Find a point estimate of the true proportion of all light bulbs that last more than

500 hours.

Solution:

Instructor Comments:

2.)

Find the critical value for

z

α

/2

that corresponds to a degree of confidence of 98%.

Solution:

Instructor Comments:

3.)

Find the critical value for

t

α

/

2 corresponding

to n = 12 and 95% confidence level.

Solution:

Instructor Comments:

4.)

Use the confidence level and sample data to find the margin of error

E

.

College students’ annual earnings:

99% confidence,

n

= 74,

x

= $3967,

s

= $874

Solution:

Instructor Comments:

5.)

Construct the confidence interval for question

4

above.

Solution:

Instructor Comments:

Name: ______________________________________

Module 2 Homework Assignment

1.) 459 randomly selected light bulbs were tested in a laboratory, 291 lasted more than 500 hours.

Find a point estimate of the true proportion of all light bulbs that last more than 500 hours.

Solution:

Instructor Comments:

2.) Find the critical value for z

α/2

that corresponds to a degree of confidence of 98%.

Solution:

Instructor Comments:

3.) Find the critical value for t

α/2 corresponding

to n = 12 and 95% confidence level.

Solution:

Instructor Comments:

4.) Use the confidence level and sample data to find the margin of error E.

College students’ annual earnings:

99% confidence, n = 74, x = $3967, s = $874

Solution:

Instructor Comments:

5.) Construct the confidence interval for question 4 above.

Solution:

Instructor Comments: