Stat 135 Winter 2008 Practice Midterm #1 (100 points) Name___________________
TA ____________________
Instructions: On questions 13-19, you MUST show your work and explain to receive full credit.
There is no need to show your work on questions # 1-12.
True/False (circle one), Multiple Choice (circle one), and Fill-in
T F 1. (2 pts) Using randomization to assign subjects to treatment groups helps to decrease
bias in the interpretation of the results.
T F 2. (2 pts) A confounding factor can confuse the interpretation of an observational study.
T F 3. (2 pts) All else being equal ... when the sample size increases so does the margin of
error.
T F 4. (2 pts) The purpose of a placebo is to reduce the variability of experimental data.
T F 5. (2 pts) If two variables have a correlation of 0.3 and you multiply every value of both
variables by 2, then the correlation at that point will be 0.6.
T F 6. (2 pts) If the standard deviation of a list of numbers is zero, then all of the numbers
must be the same.
A B C D 7. (3 pts) The use of randomization in the sampling procedure will enable a
pollster to do each of the following EXCEPT:
A) diminish bias B) calculate a margin of error
C) eliminate random sampling error D) mitigate the effects of lurking
variables
8. An analysis of car registrations in Illinois showed that about half of the
registered cars are less than 5 years old. Another result of this analysis shows that
2002 model year cars are the most common model year and that there are fewer
and fewer registered cars with each previous year.
A B C D a. (3 pts) Which of the following would describe the median age of the registered
cars in Illinois?
A) The median age is less than one year old.
B) The median age is about five years old.
C) The median age is more than five years old.
A B C D b. (3 pts) Which would describe the mean age of the registered cars in Illinois?
A The mean age is less than one year old.
B) The mean age is about five years old.
C) The mean age is more than five years old.
