Stat 104 – Homework 1
Due Friday, August 31, 2007
Reading:
August 21 – August 23
August 28 – September 6
Chapter 1
Chapter 2
Assignment:
1. Complete the following problems from the text: 1.25, 1.28, 1.32, 1.36, 1.44, and 1.54.
2. Princeton Survey Research Associates International conducted a public opinion survey on
August 1st and 2nd of 2007. 1,002 randomly selected adults from across the United States
were contacted by telephone and asked the question, “Are you satisfied or dissatisfied
with the way things are going in the United States at this time?” 24% of the people
contacted answered that they were satisfied, 69% answered that they were dissatisfied,
and 7% were unsure.
a) Identify the population.
b) Identify the population parameter of interest.
c) Identify the sample.
d) Identify a sample statistic and give its value.
e) Identify any potential sources of bias you can detect and any problems you see in
generalizing to the population of interest.
3. The following is taken from an article in the Des Moines Register, January 14, 2007,
page 4AA entitled “Study: Milk blunts heart benefits of tea.”
“There are a lot of studies that show that tea is protective against cardiac diseases,” said
lead researcher Dr. Verena Stangl, professor of cardiology at the Charite Hospital,
Universitatsmedizin-Berlin, in Germany.
“If you look at the studies, you see that in Asia there are less cardiac diseases, but in
England that’s not the case. So the question is, is the addition of milk a reason for this
difference between Asia and England, where tea is often taken with milk?” she said.
In the study, 16 healthy postmenopausal women drank either half a liter of freshly
brewed black tea, black tea with 10 percent skimmed milk, or boiled water on three
different occasions. The researchers then measured the function of the cells lining the
brachial artery in the forearm before and two hours after beverage consumption.
Stangl’s team found that black tea significantly improved the ability of the arteries to
relax and expand. “But when we added milk, we found the biological effect of teas was
completely abolished,” she said.
a)
b)
c)
d)
e)
f)
Why is this study an experiment?
What is the response variable?
What is the explanatory variable?
What treatments are compared?
Is there a placebo, e.g. a treatment with no intended effect? Explain briefly.
Is this a “blind” study, e.g. are participants not aware of which treatment they are
receiving? Explain briefly.