Note: The text mentions that if the sample size is large enough, you might use the z-distribution even if you had to estimate the population standard deviation with the sample standard deviation. That might be appropriate if you did not have access to technology; we will not do that in this class. I. The population standard deviation %u03C3 (sigma) is known. II. The population standard deviation %u03C3 (sigma) is not known, and the sample standard deviation s is used as an estimator. III. The parent population has an essentially normal distribution. IV. The parent population can have any distribution if the sample is large enough. V. The sample was obtained randomly. VI. The population mean %u03BC mu is known. VII. The data results are independent of each other. VIII. The sample size must be less than 10% of the population size. A) At %u03B1 = 0.05, we fail to reject H0. B) At %u03B1 = 0.03, we fail to reject H0. C) At %u03B1 = 0.02, we reject H0. D) At %u03B1 = 0.025, we fail to reject H0. 4. According to a study by the Centers for Disease Control, the national mean hospital stay after childbirth is 2.1 days. Reviewing records at her own hospital, a hospital administrator calculates that the mean hospital stay for a random sample of 81 women after childbirth is 2.3 days with a standard deviation of 1.2 days. Test the claim that the mean hospital stay after childbirth for this hospital is significantly longer than the national mean of 2.1 days. Identify the null and alternative hypotheses. Test the claim that the mean hospital stay after childbirth for this hospital is significantly longer than the national mean of 2.1 days. Use a 5% significance level. Using the results of your hypothesis test, determine if you reject or fail to reject and write an appropriate conclusion for this problem. A) p-value > %u03B1 Reject Ho The sample evidence do not support the claim that the mean hospital stay after childbirth for this hospital is significantly longer than the national mean of 2.1 days. B) p-value > %u03B1 Fail to reject Ho. The sample evidence do not support the claim that the mean hospital stay after childbirth for this hospital is significantly longer than the national mean of 2.1 days. C) p-value > %u03B1 Reject Ho The sample evidence do support the claim that the mean hospital stay after childbirth for this hospital is significantly longer than the national mean of 2.1 days. D) p-value > %u03B1 Fail to reject Ho. The sample evidence do support the claim that the mean hospital stay after childbirth for this hospital is significantly longer than the national mean of 2.1 days. 6. According to a study by the Centers for Disease Control, the national mean hospital stay after childbirth is 2.1 days. Reviewing records at her own hospital, a hospital administrator calculates that the mean hospital stay for a random sample of 81 women after childbirth is 2.3 days with a standard deviation of 1.2 days. Use the density tool to find a 95% confidence in.

1. Note: The text mentions that if the sample size is large enough, you might use the z-distribution
even if you had to estimate the population standard deviation with the sample standard deviation.
That might be appropriate if you did not have access to technology; we will not do that in this
class.
I. The population standard deviation %u03C3 (sigma) is known.
II. The population standard deviation %u03C3 (sigma) is not known, and the sample standard
deviation s is used as an estimator.
III. The parent population has an essentially normal distribution.
IV. The parent population can have any distribution if the sample is large enough.
V. The sample was obtained randomly.
VI. The population mean %u03BC mu is known.
VII. The data results are independent of each other.
VIII. The sample size must be less than 10% of the population size.
A) At %u03B1 = 0.05, we fail to reject H0.
B) At %u03B1 = 0.03, we fail to reject H0.
C) At %u03B1 = 0.02, we reject H0.
D) At %u03B1 = 0.025, we fail to reject H0.
4. According to a study by the Centers for Disease Control, the national mean hospital stay after
childbirth is 2.1 days. Reviewing records at her own hospital, a hospital administrator calculates
that the mean hospital stay for a random sample of 81 women after childbirth is 2.3 days with a
standard deviation of 1.2 days.
Test the claim that the mean hospital stay after childbirth for this hospital is significantly longer
than the national mean of 2.1 days.
Identify the null and alternative hypotheses.
Test the claim that the mean hospital stay after childbirth for this hospital is significantly longer
than the national mean of 2.1 days. Use a 5% significance level.
Using the results of your hypothesis test, determine if you reject or fail to reject and write an
appropriate conclusion for this problem.
A) p-value > %u03B1
Reject Ho
The sample evidence do not support the claim that the mean hospital stay after childbirth for this

2. hospital is significantly longer than the national mean of 2.1 days.
B) p-value > %u03B1
Fail to reject Ho.
The sample evidence do not support the claim that the mean hospital stay after childbirth for this
hospital is significantly longer than the national mean of 2.1 days.
C) p-value > %u03B1
Reject Ho
The sample evidence do support the claim that the mean hospital stay after childbirth for this
hospital is significantly longer than the national mean of 2.1 days.
D) p-value > %u03B1
Fail to reject Ho.
The sample evidence do support the claim that the mean hospital stay after childbirth for this
hospital is significantly longer than the national mean of 2.1 days.
6. According to a study by the Centers for Disease Control, the national mean hospital stay after
childbirth is 2.1 days. Reviewing records at her own hospital, a hospital administrator calculates
that the mean hospital stay for a random sample of 81 women after childbirth is 2.3 days with a
standard deviation of 1.2 days.
Use the density tool to find a 95% confidence interval for the mean hospital stay after childbirth
for this hospital.
What would be an appropriate interpretation of the confidence interval?
A) We are 95% confident that the confidence interval contains the sample mean hospital stay for
this hospital.
B) We are 95% confident that the confidence interval contains the population mean hospital stay
for this hospital.
C) 95% of the hospital stays for all women after childbirth fall in this confidence interval.
D) 95% of the time an individual mother's hospital stay after childbirth will fall in this
confidence interval.
7. n ActivStats, navigate to Chapter 23, homework problem BBT Coke Volumes.

3. Randomly selected cans of Coke are measured for the amount of cola in ounces. The sample
values listed below have a mean of 12.18 ounces and a standard deviation of 0.118 ounces. Use a
0.05 significance level to test the claim that cans of coke have a mean amount of cola greater
than 12 ounces.
The wording of the problem indicates that the data have been collected randomly. But we need
to check the "essentially normal" condition. Make a histogram for the variable volume. Make a
second histogram for the variable volume. For the second histogram, use the hypermenu to go to
the Plot Scale dialog box. Change the bar width from 0.1 to 0.125. Analyze the two histograms
displaying the distribution for the sample of volumes. Has the condition "essentially normal"
been met for this data?
NOTE: To find the sample size, select volume as Y and use Calc, Summaries, Report.
A) The data is unimodal and symmetric. Proceed with the t-test.
B) The data is unimodal and has a strong skew to the left. Do not proceed with the t-test.
C) The data is unimodal and has a slight skew to the left. Since the sample size is 30, proceed
with the t-test.
A is wrong
8. In ActivStats, navigate to Chapter 23, homework problem BBT Coke Volumes.
Randomly selected cans of Coke are measured for the amount of cola in ounces. The sample
values listed below have a mean of 12.18 ounces and a standard deviation of 0.118 ounces. Use a
0.05 significance level to test the claim that cans of coke have a mean amount of cola greater
than 12 ounces.
Find the p-value.
NOTE: Since the individual data values are included in the variable Volume, select Volume as Y
and then use Calc, Test. Be sure to select the correct test method, correct HO, correct HA and
significance level before clicking the Show Results button.
A) 8.532
B) 1.000
C) 0.9999
D) %u2264 0.0001

4. Thank you SOOOOO much!A.
B.
C.
D.
E.
F.
G.
H.
Solution
(1)
(D)
(2)
B) We are 95% confident that samples would show mean production between 23 and 27 items a
day.
(3)
D) At %u03B1 = 0.025, we fail to reject H0.
(4)
(A)
(5)
TEst statistics:
T=(2.3-2.1)/(1.2/sqrt(89))= 1.57233
P-value;
T(1.57233,88) =0.0597

5. B) p-value > %u03B1
Fail to reject Ho.
The sample evidence do not support the claim that the mean hospital stay after childbirth for
this hospital is significantly longer than the national mean of 2.1 days.
(6)
95 % CI:
(2.3-1.96*1.2/sqrt(89),2.3+1.96*1.2/sqrt(89))
=(2.050688,2.549312)
B) We are 95% confident that the confidence interval contains the population mean hospital stay
for this hospital.
(7)
C) The data is unimodal and has a slight skew to the left. Since the sample size is 30, proceed
with the t-test.
(8)
Ho: mean=12
H0: mean>12
TEst statistics:
T=(12.18-12)/0.118 =1.525424
p-value = 0.0636
All the options are wrong