Confidence Intervals for Two Means - UH
Confidence Intervals for Two Means
Section 7.5
Cathy Poliak, Ph.D.
cathy@math.uh.edu
Office in Fleming 11c
Department of Mathematics
University of Houston
Lecture 21 - 2311
Cathy Poliak, Ph.D. cathy@math.uh.edu Office in Fleming 11cSections
(Department
7.5 of Mathematics University of Lecture
Houston21
) - 2311
1 / 26
Outline
1
Matched Pairs For Means
2
Two Population
Cathy Poliak, Ph.D. cathy@math.uh.edu Office in Fleming 11cSections
(Department
7.5 of Mathematics University of Lecture
Houston21
) - 2311
2 / 26
Popper Set Up
Fill in all of the proper bubbles.
Make sure your ID number is correct.
Make sure the filled in circles are very dark.
This is popper number 17.
Cathy Poliak, Ph.D. cathy@math.uh.edu Office in Fleming 11cSections
(Department
7.5 of Mathematics University of Lecture
Houston21
) - 2311
3 / 26
Popper #17 Questions
Match the proper confidence interval for the examples given:
q
p?)
? s
b) x? z ? ̦n c) x? tdf
a) p? z ? p?(1?
n
n
1. An experimenter flips a coin 100 times and gets 56 heads. Find
the 96.5% confidence interval for the probability of flipping a head
with this coin.
2. An SRS of 24 students at UH gave an average height of 6.1 feet
and a standard deviation of .3 feet. Construct a 90% confidence
interval for the mean height of students at UH.
3. The gas mileage for a certain model of car is known to have a
standard deviation of 4 mi/gallon. A simple random sample of 49
cars of this model is chosen and found to have a mean gas
mileage of 27.5 mi/gallon. Construct a 96.5% confidence interval
for the mean gas mileage for this car model.
Cathy Poliak, Ph.D. cathy@math.uh.edu Office in Fleming 11cSections
(Department
7.5 of Mathematics University of Lecture
Houston21
) - 2311
4 / 26
Popper #17 Questions
4. As the length of the confidence interval for the population mean
increases, the degree of confidence in the intervals actually
containing the population mean
a) does not change
b) decreases
c) increases
5. What will reduce the width of a confidence interval?
a)
b)
c)
d)
Increase variance.
Increase confidence level.
Decrease variance.
Decrease number in sample.
Cathy Poliak, Ph.D. cathy@math.uh.edu Office in Fleming 11cSections
(Department
7.5 of Mathematics University of Lecture
Houston21
) - 2311
5 / 26
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