
(a)
Section 1:
To find: The sample proportion of the students who takes breakfast regularly.
(a)
Section 1:

Answer to Problem 16E
Solution: The sample proportion of the students who takes breakfast regularly is ˆp=0.3633_.
Explanation of Solution
Given: The randomly selected samples of 300 students are asked on their regular eating habits of breakfast. The survey showed that 109 students eat their breakfast regularly.
Explanation:
Calculation: The formula for sample proportion is defined as:
ˆp=Xn
Here,
X=number of succeses in the samplen=sample size
Substitute X=109 and n=300 in the above defined formula to get the required sample proportion. So,
ˆp=Xn=109300=0.3633
Therefore, the sample proportion ˆp is obtained as 0.3633.
Section 2:
To find: The standard error SEˆp of sample proportion ˆp.
Section 2:

Answer to Problem 16E
Solution: The standard error SEˆp of sample proportion ˆp is SEˆp=0.0278_.
Explanation of Solution
Calculation: The formula for standard error SEˆp of sample proportion ˆp and
SEˆp=√ˆp(1−ˆp)n
The sample proportion ˆp is obtained as 0.3633 in the previous part. Substitute the obtained sample proportion of 0.3633 and sample size of 300 in the standard error formula. So,
SEˆp=√ˆp(1−ˆp)n=√0.3633(1−0.3633)300=√0.231313300=0.0278
Therefore, the standard error is obtained as 0.0278.
Section 3:
To find: The margin of error for 95% confidence level.
Section 3:

Answer to Problem 16E
Solution: The margin of error for 95% confidence level is m=0.0545_.
Explanation of Solution
Calculation: The formula for margin of error m is defined as:
m=z*×SEˆp
Here, z* is the critical value of the standard normal density curve.
The standard error is obtained as SEˆp=0.0278 in previous part. The value of z* for 95% confidence level is z*=1.96 from the standard normal table provided in the book.
So, the margin of error is obtained as:
m=z*×SEˆp=1.96×0.0278=0.0545
Therefore, the margin of error is obtained as 0.0545.
(b)
Whether the guidelines to use the large-sample confidence interval for population proportion are satisfied.
(b)

Answer to Problem 16E
Solution: Yes, the guidelines are satisfied to use the large-sample confidence interval for the population proportion.
Explanation of Solution
In the provided problem of eating breakfast, the number of successes is defined as the number of students who eat their breakfast regularly. So, the number of successes is 109.
The number of failures is obtained as,
Number of failures=300−109=191
The obtained number of successes and failures shows that they are more than 10.
Therefore, the guidelines to use the large-sample confidence interval for a population proportion are satisfied.
(c)
To find: The 95% large-sample confidence interval for the population proportion.
(c)

Answer to Problem 16E
Solution: The 95% large-sample confidence interval is (0.3088,0.4178)_.
Explanation of Solution
Calculation: The formula for large-sample confidence interval for population proportion p is defined as:
ˆp±m
Here, ˆp is the sample proportion and m is the margin of error.
The sample proportion ˆp is obtained as 0.3633 and the margin of error is obtained as 0.0545 in part (a).
Substitute the values of margin of error and sample proportion in the formula for confidence interval. Therefore, the large-sample confidence interval is obtained as:
ˆp±m=0.3633±0.0545=(0.3633−0.0545,0.3633+0.0545)=(0.3088,0.4178)
Therefore, the required confidence interval is obtained as (0.3088,0.4178).
(d)
To explain: A short statement on the meaning of the obtained confidence interval.
(d)

Answer to Problem 16E
Solution: The obtained confidence interval shows that it is 95% confident that between 30.88% and 41.78% of students responded that they eat their breakfast regularly.
Explanation of Solution
(0.3088,0.4178)=(30.88%,41.78%)
This shows that there is 95% confidence that the percentage of the students who responded that they eat their breakfast regularly is lie between 30.88% and 41.78%.
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Chapter 8 Solutions
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