A survey found 195 of 250 randomly selected Internet users
have high-speed Internet access at home. Construct a 90%
confidence interval for the proportion of all Internet users
who have high-speed Internet access at home.
25%
10
1.
2.
3.
4.
25%
25%
2
3
25%
(0.719, 0.841)
(0.729, 0.831)
(0.712, 0.847)
(0.737, 0.823)
1
4
The higher the level of confidence we
want, the narrower our confidence
interval becomes.
50%
50%
10
1. True
2. False
1
2
We have calculated a 95% confidence interval for p and
pq
z
would prefer to have a smaller margin of error
n
without losing any confidence. In order to do this, we
can
25%
25%
25%
25%
I. change the z∗ value to a smaller number.
II. take a larger sample.
III. take a smaller sample.
*
10
1.
2.
3.
4.
I only
II only
III only
I and II
1
2
3
4
We have calculated a confidence interval based on a
sample of size n = 100. Now we want to get a better
estimate with a margin of error z p n q that is only onefourth as large. How large does20%
our new
need20%
20% sample
20%
20%
to be?
*
10
1.
2.
3.
4.
5.
25
50
200
400
1600
1
2
3
4
5
A news poll which estimated that 82% of all voters
believe global warming exists had a margin of error of
+/- 3%. Suppose an environmental group planning a
follow-up survey on this issue wants
determine
25% to
25%
25% a25%
95% confidence interval with a margin of error of no
more than 2%. How large a sample do they need? (For
estimate of p use 0.82)
10
1.
2.
3.
4.
32
1418
999
38
1
2
3
4
At Dartmouth College students can buy an 18 meals/week food
plan or a 14 meals/week food plan. A campus organization
10
calculated a 95% confidence interval for p, the proportion of
students with a 14 meals/week plan, as (0.58, 0.66). Choose the
25% interval.
25%
25%
25%
correct interpretation of this confidence
1. We are 95% confident that the true proportion p of students
with a 14 meals/week plan is between 0.58 and 0.66.
2. In 95% of all random samples of Dartmouth students, the
sample proportion p of students with a 14 meals/week plan
is between 0.58 and 0.66.
3. We are 95% confident that the interval (0.58, 0.66) has
captured the true proportion p of students with a 14
meals/week plan.
4. In 95% of all random samples of Dartmouth students, the
sample proportion p of students with a 14 meals/week plan
1
2
3
4
will be 0.62.