CU Probability and Normal Distribution Questions

PSYC4700 – Statistics for the Behavioral SciencesWeek 4: Probability
Complete the following problems within this Word document. (Do not submit other files.) Show
your work for problem sets that require calculations. Ensure your answer to each problem is
clearly visible. (You may want to highlight your answer or use a different font color to set it
apart.)
Submit the document to your instructor by Sunday, 11:59 p.m. central time.
Problem Set 4.1: Probability and Conditional Probability
Criterion: Compute the probability.
Instructions: Read the following and answer the questions.
Researchers are often interested in the likelihood of sampling outcomes. They may ask
questions about the likelihood that a person with a particular characteristic will be selected to
participate in a study. In this exercise, we will select a sample of one participant from the
following hypothetical student population of men and women living on or off campus. The
population is summarized in the following table.
Male
Female
Row Totals
On campus
30
25
55
Off campus
20
25
45
Column Totals
50
50
100
1. What is the probability of selecting a male participant? _______________________
2. What is the probability of selecting a female participant? ______________________
3. What is the probability of selecting a student who lives on campus? _____________
4. What is the probability of selecting a student who lives off campus? _____________
5. What is the probability of selecting a male student, given that he lives off campus?
_______________________
6. What is the probability of selecting a female student, given that she lives on campus?
_______________________
7. What is the probability of selecting a male student, given that he lives on campus?
_______________________
8. What is the probability of selecting a female student, given that she lives off campus?
_______________________
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PSYC4700 – Statistics for the Behavioral Sciences
9. What is the probability of selecting a student who lives on campus, given that he is a
male? _______________________
10. What is the probability of selecting a student who lives off campus, given that he is a
male? _______________________
11. What is the probability of selecting a student who lives on campus, given that she is a
female? _______________________
12. What is the probability of selecting a student who lives off campus, given that she is a
female? _______________________
Problem Set 4.2: Determining Probability
Criterion: Determine the probability.
Instructions: Read the following and answer the question below.
Probability of first marriage among women. A National Center for Health Statistics (NCHS) brief
report by the Centers for Disease Control and Prevention (CDC) in 2009 identified that about
6% of women in the United States married for the first time by their 18th birthday, 50% married
by their 25th birthday, and 74% married by their 30th birthday.
Based on these data, what is the probability that in a family with two daughters, the first and
second daughter will be married by each of the following ages?
1. 18 years of age:___________________________
2. 25 years of age:___________________________
3. 30 years of age:___________________________
Problem Set 4.3: Understanding Normal Distribution
Criterion: Solve problems with information about normal distributions and probabilities.
Instructions: Read the following and answer the questions.
Judging the humorousness of “lawyer” jokes. Stillman, Baumeister, and DeWall (2007)
conducted a study where participants listened to a variety of jokes. To determine how funny the
jokes were, the researchers asked a group of 86 undergraduates to rate the jokes on a scale
from 1 (very unfunny) to 21 (very funny). Participants rated a “lawyer joke” as one of the funniest
jokes, with a rating of 14.48 ± 4.38 (M ± SD).
Assuming that these data are normally distributed:
1. What was the rating that marks the cutoff for the top 10% of participant ratings for this
joke? ___________________________
2. How many of the 86 undergraduates gave the joke a rating of at least 10?
___________________________
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PSYC4700 – Statistics for the Behavioral Sciences
Problem Set 4.4: Calculating z Scores in SPSS
Criterion: Calculate z scores using SPSS.
Data: The following is a list of how senior citizens rated the Internet on a 1–10 scale, with 1
being “really distrust it” and 10 being “completely trust it”: 8, 9, 4, 6, 8, 5, 1, 9, 7, 6
Instructions: Complete the following steps:
a. Enter the data into SPSS using the variable name Rating.
b. In the Toolbar, click Analyze, select Descriptive Statistics, and then select
Descriptives.
c. Select Goals and then click Arrow to send data over to the right side of the table. Check
the box Save Standardized Values as Variables.
d. Select Options, check the boxes Mean and Standard Deviation, and then deselect all
other boxes. Click Continue.
e. Click OK and then copy and paste the descriptive statistics table below.
f. Go to the Data View in SPSS. You will see that the z scores have been added to the file.
Paste a screenshot of the Data View, showing the z scores, into the Word document.
g. Answer: Which number of goals is closest to the z score of 0?
Problem Set 4.5: Define Problem for Final Paper
Criterion: Define a problem in the social sciences.
Instructions: Write a well-written paragraph that includes the following:
a. Topic sentence establishing the topic and variables.
b. Evidence of what the problem is.
c. Evidence of how many people have the problem.
Problem Set 4.6: Literature Review, Part 1
Criterion: Synthesize sources.
Instructions: Write two well-written paragraphs that include the following:
a. Topic sentence with main idea.
b. Evidence from at least two different sources that support the main idea.
c. An analysis explaining how the evidence relates to the topic sentence or how the main
idea relates to the problem (established in Problem Set 4.5).
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