Stat 104 – Homework 5
Due Thursday September 29, 2011
Reading:
September 22 – September 29
Chapter 4
Assignment:
1. Complete the following problems from the text: 4.3, 4.7, 4.8, 4.15, 4.20, 4.21, 4.37,
and 4.39.
2. Below is a list of 10 individuals who wish to attend the national FFA convention.
There is only enough money to send three. To be fair the three will be chosen at
random.
Angela
Jamil
Juan
Kathryn
Steve
Samantha
Lindsay
Joshua
Mark
Melanie
Using the line from the random number table below, explain how you would select
the three individuals to go. Actually indicate which three individuals are selected
using your scheme.
36994 98872 31016 56420
3. An article in the Des Moines Register on March 3, 2010 reported on a study linking
hearing loss to the use of analgesics (painkillers). Below are excerpts from that
article.
New research suggests that regular use of aspirin, acetaminophen and
other analgesics can substantially increase the risk of hearing loss,
especially in men younger than 50.
Researchers report in the American Journal of Medicine that use of
acetaminophen more than twice a week by such men doubles the risk of
hearing loss; use of ibuprofen and related drugs increases the risk by
nearly two thirds; and regular use of aspirin increases it by about a third.
Dr. Sharon Curhan of Brigham and Women’s Hospital in Boston and her
colleagues studied 26,917 men enrolled in the Health Professionals
Follow-up Study. Their ages ranged from 40 to 75 at enrollment in 1986.
Every two years, the men filled out questionnaires about their use of
various drugs, as well as other lifestyle factors. They also get a complete
physical every two years.
a) Why is the Health Professionals Follow-up Study an observational study and not
an experiment? Explain briefly.
b) Is the Health Professionals Follow-up Study a prospective or a retrospective
study? Explain briefly.
c) What is the explanatory variable? Is this categorical or numerical?
d) What is the response variable? Is this categorical or numerical?
e) Based on this study, does the use of analgesics (painkillers) cause hearing loss?
Explain briefly.
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4. The following is excerpted from a Des Moines Register article that appeared Sunday,
September 27, 2009.
Study finds antennas are key to monarch butterfly navigation.
Millions of monarch butterflies migrate to Mexico for the winter; and
scientists have long speculated on how the insects find their way. It turns
out that their antennas are the key. How do we know? Researchers
painted butterfly antennas black, and the insects got lost. The researchers
… did the test by holding the butterflies’ wings gently and dipping their
antennas in enamel paint. The ones with black paint were unable to orient
to the south … while butterflies whose antennas were coated with clear
paint had no trouble navigating. Because the animals with black paint got
lost even though their eyes were able to see light, the researchers
concluded the antennas were vital for navigation.
a)
b)
c)
d)
e)
f)
Why is this study an experiment and not an observational study?
Who are the subjects in the experiment?
What is the response variable? Is this variable categorical or numerical?
What are the treatments?
Is there a control group in the experiment? Explain briefly.
Suppose there were 100 butterflies in the experiment, explain briefly how
butterflies should have been assigned to treatments. Your explanation should be
complete enough so that a person not knowledgeable in statistics could follow
your explanation and actually assign the butterflies to the treatments.
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