Study Guide for:
Introductory Statistics for the Behavioral Sciences (7th Edition)
Joan Welkowitz, Barry H. Cohen, and R. Brooke Lea
Preface: This study guide was prepared by Grace Jackson and Samantha Gaies, both of whom
have served as TA’s for Barry Cohen’s Master’s Statistics course at New York University.
Although they are otherwise quite normal, and even fun to be with, both happen to love learning
and teaching statistics. They have used hair color as a variable in at least one example, because
Grace is a blonde, whereas Samantha is a brunette, and both share a great sense of humor about
people’s differences. As of this writing, Grace is in her first year of a doctoral program in Social
Psychology at UCLA, while Samantha is in her second year of a doctoral program in Counseling
Psychology at UT-Austin.
Chapter 1: Introduction
Statistics helps you describe and better summarize numbers, and can even help you to make
assumptions about the greater population, when you can measure only a small sample of
individuals.
1. Descriptive and Inferential Statistics
Descriptive statistics are used to describe the group of individuals that you have in front of
you. Inferential statistics allow you to make inferences about the larger population that
interests you.
For example, you want to know if women really do cry more often than males while
watching chick flicks. You can’t measure the entire population of women (it would take
forever!), but you can test a group of 100 randomly sampled men and women and measure
the minutes they spent crying at the same sad movie. Then by using statistics, you can draw
an inference about the population (i.e., make generalizations about the entire population of
men and women based on your sample).
2. Populations and Samples
Population: The entire group that you are interested in. This could be very general—e.g., all
people in the world—or specific—e.g., just blue-eyed guys in their 30s from Texas.
Sample: A selection of people (cases, observations, etc.) from a larger population—e.g.,
1,000 of the roughly 6.8 billion people in the world, or just 50 of those approximately
300,000 blue-eyed Texan gentlemen.
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Population
The entire Introductory Psychology class
All of the classes in the Psychology
Department
All departments within the university
Sample
A subset of students in the Introductory
Psychology course
A subset of psychology classes
A subset of departments within the university
One number that summarizes a bunch of numbers in a sample is called a statistic. The same
kind of summary applied to a population is called a parameter.
3. Measurement Scales
The four measurement scales can be represented by NOIR, that is, N for Nominal, O for
Ordinal, I for Interval, and R for Ratio.
Here is your first exercise:
1. Using the first letter of each type of scale, label each of the variables below, in the space in
front of it, with the type of scale that would most likely be used to measure that variable.
___Hair Color of Hipsters
___Temperature (Kelvin)
___Temperature (Fahrenheit)
___Temperature (Sunny to Rainy)
___Gender
___Likert Scale (1 to 7)
___Minutes Spent on Facebook per Week
___ # of Siblings
___Car Colors
___Likert Scale (Disagree Strongly to Agree
Strongly)
___Cost of Overpriced Pair of Jeans
___Shoe Size
___Weight of Sumo Wrestlers
___Karats of Bling on Rapper du Jour
___Attractiveness Ratings (Hot to Not)
___Attractiveness Ratings (1 to 10)
___# of Text Messages Sent per Day
___Movie Genre
___Height of America’s Next Top Model
Contestants
4. Independent and Dependent Variables
2. For each of the proposed experiments below, identify the Independent Variables (IV), as
well as the Dependent Variable (DV):
a. Women are assigned to conditions in which they are presented with the photo of a male,
and each time a different cologne scent is sprayed. After each presentation, they are asked to
rate the attractiveness of the male.
b. Men are asked to perform karaoke of “Oops! . . . I Did It Again” by Britney Spears in
front of a live audience and receive either positive (screaming and whistling) or negative
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(booing) reinforcement. Afterward, the singer is asked to rate his success in his performance,
and how much he would want to do it again.
c. New puppies are being trained to sit. They are randomly assigned to trainers (nice or
strict) and to differing reward treats (bacon or peanut butter). The number of minutes it took
for the puppy to learn to sit on command was recorded.
d. Researchers are interested to see how well they can predict success in the Miss USA
Pageant based on minutes spent in the tanning booth.
e. Minutes spent watching The Hills are recorded for college freshmen to investigate if a
correlation exists with their GPA at the end of the year.
5. Summation Notation and Rules
3. For the following summation exercises, the X values are 3, 2, 1, 4.
a. What is the value of ΣX?
b. What is the value of ΣX2?
c. What is the value of (ΣX)2?
d. What is the value of Σ(X + 1)2?
4. For the following summation exercises, the X values are 5, 1, 3, 2, and the Y values are 1,
4, 2, 6, in the same order.
a. What is the value of Σ(X + Y)?
b. What is the value of ΣXY?
c. What is the value of (ΣX)(ΣY)?
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Answers to Exercises
1.
N___Hair Color of Hipsters
R___Temperature (Kelvin)
I____Temperature (Fahrenheit)
O___Temperature (Sunny to Rainy)
N___Gender
I____Likert Scale (1 to 7)
R___Minutes Spent on Facebook per Week
R___# of Siblings
N___Car Colors
O___Likert Scale (Disagree Strongly to Agree Strongly)
R___Cost of Overpriced Pair of Jeans
I____Shoe Size
R___Weight of Sumo Wrestlers
R___Karats of Bling on Rapper du Jour
O___Attractiveness Ratings (Hot to Not)
I____Attractiveness Ratings (1 to 10)
R___# of Text Messages Sent per Day
N___Movie Genre
R___Height of America’s Next Top Model Contestants
2. a. IV: type of cologne sprayed; DV: male attractiveness ratings
b. IV: type of reinforcement; DV: self-rated success of performance
c. IVs: style of trainer and type of doggie treat; DV: minutes to learn to sit
d. IV: minutes in tanning booth; DV: success in pageant
e. IV: minutes watching TV; DV: GPA
3. a. 10
b. 9 + 4 + 1 + 16 = 30
4. a. 6 + 5 + 5 + 8 = 24
c. 102 = 100
b. 5 + 4 + 6 + 12 = 27
d. 42 + 32 + 22 + 52 = 54
c. 11 * 13 = 143
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