Political Science 30, Political Inquiry, Homework Project #2
Part A. Sampling and Polling Statistics
Question #1. [30 points total] I want to find out how Donna Frye and Jerry Sanders will do
in Tuesday’s election. So I leave class and spend this nice, sunny day at La Jolla Shores,
setting up a booth and asking the first 500 people who pass by if they are registered voters
and, if so, whether they prefer Frye or Sanders.
a. Do you think that the sample statistics from this study will closely approximate
the population parameters? If not, use two terms that we have learned in this
course to tell me what is wrong with my sampling scheme. (These terms should
not include “sampling bias” or “sampling variability.”) [16 points. Where to
start? The sample could include many people who are not in the population
(those who are not city residents and are just spending a day at the beach). Of
the members of the population, this will not be a random sample. It’s a
convenience sample because I just go to a convenient location for me, and it’s also a
voluntary response sample because only the people who chose to talk to me get
sampled. Students get 8 points for each example of a problem, linked to a term].
b. Will my sampling scheme lead to sampling bias? Will it lead to sampling
variability? Explain. [14 points. 7 for showing why it should lead to sampling
bias in a way that demonstrates that students know that sampling bias occurs
when the sample is not representative of the population. 7 points demonstrating
knowledge of what sampling variability is and making a cogent argument either
way, since repeating this bad poll might lead to consistently wrong findings or
might jump all over the place. If they answer that there is no sampling variability
because I only conduct one poll, subtract three points and remind them that
sampling variability can still be a problem because it is about the potential to get
different statistics from different samples, based on my sampling scheme. The
fact that I am lazy and only conduct one poll does not solve my sampling
variability problem.]
Question #2. [20 points] The Field Poll came out today and reported that only 27% of
voters currently support Proposition 76, which would impose a spending cap in California.
The figure is based on the responses of 1,087 voters. Assuming that the poll drew a truly
random sample, what is the margin of error for this estimate? (State your final answer in
percentages, after converting to proportions in order to calculate the margin of error. Feel
free to use a calculator, but be sure to show your work.)
27% + or – 2.7% (if they round to 3%, that is fine). 10 points for getting the formula right,
15 if their only mistake was not converting to proportions.
[20 points total] Question #3. A President’s power is hard to define: we generally know a
powerful President when we see one, but political scientists like to find systematic ways to
measure presidential power.
a. In one sentence, provide a conceptual definition of “presidential power.” [5
points for a sensible definition that is not circular.]
b. Write out an operational definition that is specific enough that any other
researcher could go out and collect information to measure your concept of
presidential power. [15 points for one that fits with the concept they state and is
sufficiently specific.]
Part B. Data Project
[30 points total] Question #4. This step of the data project asks you to use the SPSS
software to open up the dataset that you chose. You are going to use the same hypothesis
that you proposed in Homework Project #1, unless your TA has suggested that you use a
revised hypothesis. Please use the “World” or “States” SPSS datasets that are on the course
website.
a. [15 points. 5 points for getting the type of variable correct, 5 points for an
appropriate measure of central tendency, and five points for an appropriate
measure of dispersion. Only the mode is appropriate for a nominal or ordinal
variable. Subtract two points if they give you all measures of central tendency
rather than picking one.] Pick one of your independent variables. Tell us
whether it is a nominal, ordinal, interval, or ratio variable. “Describe” it by
giving us a measure of central tendency (mode, median, or mean) AND a
measure of dispersion (range or standard deviation) that you think is appropriate.
Let SPSS calculate these for you.
b. [15 points. 5 points for getting the type of variable correct, 5 points for an
appropriate measure of central tendency, and five points for an appropriate
measure of dispersion. Use this as a chance to make sure that their DV is
interval or ratio.] Provide the same information (type of variable, measure of
central tendency, measure of dispersion) for your dependent variable.