Statistics 101 – Homework 5
Due Friday, October 7, 2005
Homework is due on the due date at the end of the lecture.
Reading:
September 30
October 3 – October 7
Chapter 11
Chapters 12 & 13
Assignment:
1. Harris Interactive® conducted a public opinion survey between June 17 and 21, 2005.
1,000 randomly selected U.S. adults were contacted by telephone and asked the question,
“Do you think human beings developed from earlier species or not?” 38% of the people
contacted answered “Yes, I think human beings developed from earlier species.” 54%
answered “No, I do not think human beings developed from earlier species.” and 8%
were either not sure or declined to answer.
a) Identify the population.
b) Identify the population parameter of interest.
c) Identify the sample.
d) Identify the sampling method, including whether or not randomization was
employed.
e) Identify any potential sources of bias you can detect and any problems you see in
generalizing to the population of interest.
2. The Story County Board of Supervisors is thinking about enacting an ordinance that
would require the registration of beer kegs sold in Story County. The Board of
Supervisors wishes to get input from ISU students on the proposed ordinance. Listed
below are some ideas proposed for gathering data on ISU students’ opinions of the
ordinance. For each, indicate what kind of sampling strategy is involved and what (if
any) biases might result.
a) Put an ad in the Ames Tribune asking students to log their opinions on the Board
of Supervisors web site.
b) Hold public forums and tally the opinions expressed by those ISU students who
attend the forums.
c) Visit the Keg Shop and ask ISU students coming in to buy beer their opinions.
d) Select a dorm on the ISU campus at random and contact every resident in the
dorm to get his/her opinion.
e) Randomly select 100 ISU students from the ISU directory and contact them by
phone to get their opinions.
f) Ask the Registrar to select every 250th student, starting with the 111th student, on
the list of all students enrolled at ISU and provide addresses, phone numbers and
emails so that those students selected can be contacted to get their opinions.
3. Below is a list of 10 individuals, name and gender. We wish to select 2 individuals at
random from the list of 10.
0 Kaeli (F)
5 Kristi (F)
1 Ryan (M)
6 Dawn (F)
2 Lindsey (F)
7 Alisha (F)
3 Jon (M)
8 Juan (M)
4 Matt (M)
9 Amy (F)
a) Use the table of random numbers in the back of your text (row 10 starting from
the left) to select a simple random sample of two individuals. Who are those two
individuals?
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b) Describe how you would randomly sample to ensure that there would be one
male (M) and one female (F) chosen.
4. The following excerpt is taken from an article that appeared in the Des Moines Register
on Wednesday, September 25, 2002.
Aspirin-like drugs may cut Alzheimer’s risk, study finds.
Taking aspirin and other anti-inflammatory medications for at least two years may reduce
the risk of developing Alzheimer’s disease, according to a study. The study, which
enrolled 5,092 Utah residents 65 and older and followed them for several years,
examined anti-inflammatory medications, including ibuprofen and naproxen. Patients
taking an anti-inflammatory medication for at least two years developed Alzheimer’s at
roughly half the rate of nonusers. The results were nearly as strong for those who used
aspirin regularly. One drawback is that the study involved a community of primarily
Mormon residents, who tend to live more healthily.
a)
b)
c)
d)
e)
Why is this an investigative study and not an experiment?
Is it a retrospective or prospective study?
Who were the subjects studied?
What is the parameter of interest?
Why is it a drawback that the study involved a community of primarily Mormon
residents?
5. The following excerpt is taken from an article that appeared in the Des Moines Register
on Saturday, March 4, 2000.
Study: Meditation helps clear clogged arteries
Transcendental meditation to reduce stress helped clear clogged arteries in a group of
African-Americans, a study published Friday shows. The study used ultrasound to
measure the thickness of the carotid artery wall in 60 blacks. The researchers recruited
60 African-American men and women with high blood pressure in the Los Angeles area.
One group was taught transcendental meditation and practiced it for 20 minutes twice a
day. A second group received health education, then spent 20 minutes, twice a day,
engaged in leisure activities such as reading or exercise. After seven months, the
meditating group had a mean reduction in artery wall thickness of 0.098 mm. The wall
thickness in the control group increased by 0.054 mm.
a)
b)
c)
d)
e)
f)
Why is this an experiment?
Identify the subjects studied.
Identify the factor(s) in the experiment.
Identify the treatments.
Identify the response variable measured.
The design is not specified in the article. Explain how this study would be conducted
if it were a completely randomized design.
g) Is the experiment blind (or double-blind)?
h) Discuss the scope of the conclusion the experiment can reach.
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