Stat 1001 Section 4, Fall, 2001

Sample Exam #1 Questions

These questions are borrowed from another instructor using your textbook.  Your exam will have similar questions.  The exam is closed book, but you may have one page (two-sided) of notes. 

1. "Stroke risks:  Young women who suffer from migraines have at least three times the risk of suffering stroke as those who do not, say French researchers.  The danger is further increased for those who take the Pill or smoke, although the absolute risk for young women is low.  Christophe Tzourio and colleagues from INSERM, France’s national agency, make the links after studying 245 women between 18 and 45 years old.  Of these, 72 had suffered an ischaemic stroke [localized obstruction of the inflow of blood] and 173 were chosen at random as controls.  Women who had migraines with auras---warnings that their headaches were about to start---had a risk of stroke six times that of women who did not have migraines.  Women who had migraines without auras had three times the risk.  Strokes were more common among women who smoked more than 20 cigarettes a day and also among those taking a Pill with a high dose of estrogen.  In last week’s issue of the British Medical Journal, Tzourio suggests that women with migraine should be advised not to smoke and to use a low-estrogen Pill."
   1. What type of study is the paragraph describing?
   2. What is/are the explanatory variables?
   3. What is/are the response variables?
   4. Give an example of an interacting variable in this study, and explain what it means to say that the variable is an interacting variable.
   5. Is this study retrospective or prospective?  Explain.
   6. Give a example of a potential confounding variable in this study. [The study itself may not give the confounding variable; you may need to supply it yourself.]
2. Explain the difference between volunteer response and volunteer sample.  Explain which is worse and why.
3. A doctor has invented a new technique for attaching arterial grafts in emergency situations. In 40 operations, she has had 30 patients survive. She is seeking FDA approval for her procedure. Explain why this information either is, or is not, compelling, and what other information should the FDA require to make a decision.
4. Explain which of the "difficulties and disasters" given for experiments is most likely to be a problem for the following experiment, and why.  A company wants to know if placing green plants in workers’ offices will help reduce stress.  Employees are randomly chosen to participate, and plants are delivered to their offices.  One week later, all employees are given a stress questionnaire and those who received the plants are compared with those who did not.
5. Explain why it is important to know the approximate size of the sample when you read a study that tells you, for example, the proportion of a sample that is in favor of some particular candidate.