1 HOMEWORK ANSWERS
Important note about homework: Please be sure you submit your homework questions in order, and you make
it obvious which questions you are answering. In an effort to save paper, you do not need to submit the
questions; you only need to submit your answers. Please be clear and concise when preparing your homework
assignment.
Important note about late homework: Late homework is to be turned into Say Young Kim either in person,
during class, during his office hours, or by placing it in his mailbox. If you put your homework in Say Youngs
mailbox, send him an e-mail immediately afterwards to notify him of such and to document when you turned in
your homework. It is your responsibility to turn your homework in to Say Young. Thus, other TAs will not
relay your homework to him.
Important note about early homework: If you anticipate not being able to turn in your homework before
lecture on the day that it is due, you may turn your homework in early. As is the case with turning in late
homework, early homework is also to be turned into Say Young Kim following the same procedure as described
above for late homework.
When reading this homework answer key: The grading TAs have inserted comments in this key to help give
you a better understanding of mistakes and errors that may have been made. Please pay attention to these
comments; they will help you understand why an answer is considered incorrect.
1. List a belief that you hold to be true. Determine how you know this belief to be true. Use the labels
for ways of knowing that we discussed in class.
As long as you have provided a coherent belief you were given credit. For full credit you needed to
discuss how one of the following criterion was used for you to come to believe your statement in number
one is true:
a. Authority
b. Rationalism
c. Consensus
d. Experience
e. Observation
f. Scientific Method
Grading Note: Some students merely listed a few or all of the labels instead of describing/applying the labels to
their listed beliefs. For example, they would say I believe this to be true due to authority and general
consensus instead of a more correct answer of I believe this to be true because authority figures such as
politicians, historians and doctors have made public statements and wrote textbooks stating this belief to be
true. In order to receive full credit, students must have explained the criterion used for knowing the belief to
be true.
2. For each of the following, indicate whether a variable or a constant is being described:
a. The number of ounces in a gallon
i. Constant
b. The depression you feel when stats class is over
i. Variable
c. The number of students enrolled in PSYC200
i. Variable
d. The amount of coffee you drink each morning
i. Variable
e. The number of tweets you make in an hour
i. Variable
f. The number of seconds in a minute
i. Constant
3. For each of the following, indicate whether a continuous or a discrete variable is being described:
a. The number of students in stats class
i. Discrete
b. A persons weight
i. Continuous
c. The number of people who own Starbucks gold cards
i. Discrete
d. A womans pregnancy status
i. Discrete
e. An eyewitnesses choice in a lineup
i. Discrete
f. A persons SAT score
i. Continuous
4. You are at a dinner party and someone is complaining about the fact that Casey Anthony was not found
guilty for the death of her child. The party guest states that Casey was not found guilty because she was
a woman and that women are more likely than men to be found not guilty in court due to lingering patri archal views towards women. Since you are becoming an accomplished scientist, you decide to investig ate this claim. You get 250 undergraduates from the University of Maryland to act as mock jurors. One
hundred and twenty five of these people evaluate the trail of a woman defendant, and the other 125 eval uate the trial of a male defendant. Both the female and male defendants provide the same trial responses.
You record the final verdicts of the jurors and find that 75% of the jurors voted to convict the female
defendant and 28% of the jurors voted to convict the male defendant.
a. Is this an experiment? Why or why not? If this is not an experiment, please classify what this is
called.
i. This is an experiment because a variable was manipulated: The sex of the defendant was
either male or female.
Grading Note: One error that a few people made here was stating that this was either a correlational or a
naturalistic observation study. The problem clearly states that you manipulated a variable in this case the
variable of interest was the gender of the defendant which means that this is an experiment. Manipulation
was a required word to earn full credit.
b. Identify the hypothesis under evaluation.
i. The hypothesis under evaluation is that female defendants are more likely to be found not
guilty than male defendants.
Grading Note: Hypotheses are statements, not questions.
c. Identify the population in question.
i. There are a few potentially correct populations:.
1. Jury eligible people
2. College students who are jury eligible
Grading Note: Many students incorrectly stated that the population was men and women for this experiment.
The males vs. females aspect comes in with the manipulated variable.
d. Identify the sample in question.
i. The 250 undergraduates form the University of Maryland.
Grading Note: To receive full credit, you must include the number, undergraduates, and UMD.
e. List two sampling methods.
i. Convenience sampling
ii. Random sampling
Grading Note: Please note that biased and nonrandom sampling are not valid sampling methods.
f. Describe how the researcher may have used each sampling method for this example.
i. If the research used convenience sampling the researcher may have sampled 250 friends.
ii. If the researcher used random sampling the researcher may have used a lottery system
whereby each person in the population is assigned a number and then the researcher
selects numbers at random and those people are in the sample!
Grading Note: Many students confused random sampling with random assignment. Randomly assigning
treatment does not correct for a sample that was not selected randomly. You must have included enough detail
to prove you understand the sampling method to get full credit.
g. What does having a biased sample mean?
i. A biased sample is one in which the sample is not representative of the population of
interest there is a discrepancy between the sample and the population.
Grading Note: Some students incorrectly stated that a biased sample means that the participants in the sample
have personal biases. Please review the definition of a biased sample.
h. Is the current sample biased? If so, how?
i. This may or may not be a biased sample it depends on what you specified as your
population of interest.
1. For example, if you specified that the population of interest was all jury eligible
people then you would a have biased sample: Because your sample does not
represent all of the people that are jury eligible as your sample over-represents
young, educated people.
2. If you specified that your population of interest was jury eligible college students
then your sample is not biased as your sample is jury eligible college students so
it represents your population well.
Grading Note: To get full credit, your answer to (h) must correspond and refer to your stated population in
(c).
i. What is the best sampling method? Why?
i. The best sampling method is the method that produces least biased samples and that
would occur with random sampling. With random sampling we assume that the
probability of selecting a biased sample is so low that it rarely, if ever, happens.
j. Identify and classify (independent or predictor vs. dependent or criterion) the variables of interest.
i. Independent variable: Sex (male or female) of defendant.
ii. Dependent variable: Verdict outcome (guilty or not-guilty).
k. Is there a statistic(s) used in this example. If so, identify the statistic(s) in this example.
i. There are two statistics in this example: The percentage of mock jurors who voted guilty
for the male defendant (28%) and the percentage of mock jurors who voted guilty for the
female defendant (75%).
Grading Note: To get full credit, both of the statistics (28% and 75%) must be included explicitly.
l. Are there any parameters in this example? If so, identify the parameter(s) in this example.
i. There are no stated parameters in this example.
m. Does it appear that your dinner guest was correct? Why or why not?
i. It does not appear that the dinner guest was correct as a larger percentage of the mock
jurors wanted to convict the female defendant (75%) as compared to the male defendant
(28%), which is exactly the opposite of what your dinner guest predicted.
5. You have observed and recorded the frequency judgments of 9 people in your class of how often they
check facebook each week during the school year (X) and during the summer (Y).
______X__________Y_____
32
58
38
60
79
67
33
52
23
51
25
43
26
25
Perform the following mathematical operations on the above dataset:
N
a.
X
i
= 32 + 38 + 79 + 33 + 23 + 25 + 26 = 256
i=1
N
b.
(3Y ) + 1 = [(3 * 58) + (3 * 60) + (3 * 67) + (3 * 52) + (3 * 51) + (3 * 43) + (3 * 25)] + 1 = 1068 + 1 = 1069
i
i=1
N
c.
d.
X
2
i
= 32 2 + 382 + 79 2 + 332 + 232 + 252 + 26 2 = 11628
i=1
N
(X Y )
ii
2
= (32 * 58)2 + (38 * 60 )2 + (79 * 67)2 + (33 * 52 )2 + (23 * 51)2 + (25 * 43)2 + (26 * 25)2 = 42557695
i=1
5
e.
(X Y )
i =1
ii
2
= (32 * 58) 2 + (38 * 60) 2 + (79 * 67) 2 + (33 * 52) 2 + (23 * 51) 2 = 40979570
Grading note: Many students did not show their work for the problem and therefore it was difficult to see
where the errors were. For those that did show their work the errors were mostly because they did not square
each multiplication set of x*y and then add them all together for the last question, but rather square the end
product which gave them a much lower number. Additionally, please note for (b) that the 1 is outside of the
parentheses, so it must be added AFTER the summation of 3Yi. Remember, if there are parentheses to do the
operations in parentheses first! For these problems, in which work must be shown, it would be appropriate to
list all digits; using scientific notation here would not be appropriate, particularly if you rounded to only two
decimal places.
6. Imagine that you are interested in studying the impact of meditation on speech performance. For each
design specified, indicate whether you are dealing with independent variables, dependent variables, pre -
dictor variables, or criterion variables. For the types of variables present in your design, indicate which
variable corresponds to which classification (i.e., discrete or continuous). Additionally, specify a popula tion of interest and specify a sample you might procure.
a. Design an experimental design that targets this question.
i. This should have a design in which there is an independent variable that is manipulated
and a dependent variable that is measured. Here the independent variable should be
something along the lines of meditation and the dependent variable something along the
lines of speech performance. Accept answers that measure 'speech performance' as anything reasonable. In the example, 'speech performance' is operationalized as quality of
oral speech to a crowd, but any measure of speech performance could be used, such as
enunciation or anything else reasonable.
ii. An example might be having half of your sample perform mediation and the other half of
the sample will not perform meditation. Then everyone gives a five-minute speech and
you rate the quality of the speech performance on a 1-100 scale.
1. Here the independent variable is meditation (performed or not performed) and
the dependent variable is speech quality as rated by the researcher. In this case
the independent variable is a discrete variable with either meditation or no meditation while the dependent variable is a continuous rating.
2. The population of interest would be any one who has to perform a speech in college and the sample that you might use could be from communications classes in
Universities across the country.
Grading Note: In order to get full credit, independent variable and dependent variable, as well as how
both would be measured, must be clearly described. The variables must be correctly classified. The population
and sample must be stated. For this experiment, it is crucial that subjects are randomly assigned to a treatment group. Additionally, your sample size should be large enough; it is impossible to draw conclusions about
anything from a study with only one person in each group. (One person simply could be better at speeches.)
b. Design a non-experimental design that targets this question.
i. This should have either a correlational or a naturalistic observation study design. More
likely and reasonably this should be a correlational design where meditation and speech
quality is measured.
ii. An example might be to survey the people before giving speeches in a communications
class as to how often they mediate in a month and then rating their speech quality on a 1100 scale.
1. In this example the predictor variable would be the amount of meditation that a
person performs in a month and the criterion variable would be speech quality.
The predictor variable and the criterion variable here would both be continuous.
2. The population of interest would be any one who has to perform a speech in college and the sample that you might use could be from communications classes in
Universities across the country.
Grading Note: In order to get full credit, predictor variable and criterion variable, as well as how both
would be measured, must be clearly described. The variables must be correctly classified. The population and
sample must be stated.