MATH 218 SI Session (Fall 2008)
Week 13 Worksheet (11/17 – 11/23)
SI Leader: Joy Chen
[email protected]
Professors Lin & Song
www.usc.edu/si
Lin & Song Combined Worksheet
Topics Stressed: Hypothesis Testing (Week 1 of 2)
1.
Use the following data to determine whether or not to reject the null hypothesis:
Xbar = 160;
σ
= 36;
n = 36;
H
0
: μ
≤
140;
H
1
: μ > 140;
α
= 0.05
2.
We want to perform the hypothesis test: H
0
: μ = 30
H
1
: μ
≠
30
Assume the population is normally distributed and
σ
= 4.5. Sample of size 25 is selected and Xbar is 32.5.
a.
At 2% significance level?
b.
At 0.5% significance level?
3.
Mark is conducting a research on the height of the male population. From other studies, he knows that the
height of the male population is normally distributed with standard deviation of 25cm. In order to test if the
average height of the male population is greater than 175cm, he randomly picks 100 people, measures their
heights and finds the average to be 180cm. Is the average height greater than 175cm? Use a significance level
of
α
=0.03.
a.
Solve using the rejection region method.
b.
Solve using the pvalue method.
4.
In recent years, a number of companies have been formed that offer competition to AT&T in longdistance
calls. All advertise that their rates are lower than AT&T’s, and as a result their bills will be lower. AT&T has
responded by arguing that for the average consumer, there will be no difference in billing. Suppose a statistics
practitioner working for AT&T determines that the mean and standard deviation of longdistance bills for all
its residential customers are $17.09 and $3.87, respectively.
He then takes a random sample of 100
customers and recalculates their last month’s bill using the rates quoted by a leading competitor and finds it
to be $17.55. Assuming that the standard deviation of the population is the same as for AT&T, can we
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview.
Sign up
to
access the rest of the document.
 Fall '08
 HE
 Math, Statistics, Probability, Null hypothesis, Hypothesis testing, Statistical hypothesis testing, Type I and type II errors

Click to edit the document details