Practice First Midterm Exam
Statistics 200 Spring 2008 (Pfenning)
This is a closed book exam worth 150 points. You are allowed to use a calculator and
a two-sided sheet of notes. There are 8 problems, with point values as shown. If you want
to receive partial credit for wrong answers, show your work. Don’t spend too much time on
any one problem.
1. (25 pts.) An article entitled Prevent Migraines Naturally states that “Patients
who took 100 milligrams of the supplement Coenzyme Q10 (CoQ10) three times a day
had up to 50 percent fewer migraines and less nausea after three months, finds a new
Swiss study. Their headaches were also shorter and not as severe. Researchers believe
that CoQ10 prevents migraines by boosting energy production in cells.” Identify each
of the following as well as you can.
(a) explanatory variable
(b) explanatory variable type: (i) quantitative (ii) categorical (iii) not clear
(c) response variable
(d) What comparison is being made?
i. patients who do or do not take CoQ10
ii. patients before and after taking CoQ10
(e) Which one of the following additional pieces of information would be most helpful
in deciding whether CoQ10 is really beneficial for migraine sufferers?
i. Was there a control group taking a placebo?
ii. Were the patients randomly chosen to participate in the study?
iii. How did researchers define a migraine?
iv. Were different dosages of CoQ10 tested?
v. How realistic was the setting?
2. (20 pts.) Researchers are interested in how pesticides affect children’s health. Here are
designs for two actual studies:
Design A: The EPA proposes to pay each family in their study $970, some children’s clothing
and a camcorder in exchange for their participation for two years, during which they would
use various household pesticides and have their children tested for absorption rates.
Design B: A study will recruit and enroll participants in 96 locations over the next four
years and track them from conception through their children’s 21st year. The 2.7 billion
dollar study will monitor the children’s health, along with pesticide exposures in the air,
food, and water.
(a) Which design is an observational study? (i) A (ii) B (iii) both (iv) neither
(b) Which design is more vulnerable to confounding variables?
(i) A (ii) B (iii) both the same (iv) neither
