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Psychology
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PSYC 210
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Cathy Mc Farland
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Chapter 1

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Psychology

PSYC 210

Cathy Mc Farland

Fall

Description

Chapter 1 – Displaying the Order in a Group of Numbers Using Tables and Graphs
Statistics – branch of math that focuses on organization, analysis, interpretation of a group of numbers
Branches of Statistical Methods
1. Descriptive statistics – summarizes and describes a group of numbers from a research study; makes a
group of numbers easily understandable with the help of graphs and tables. (Chapter 1-2)
2. Inferential statistics – draws conclusions and makes inferences that are based on the numbers from a
research study but go beyond the numbers; uses “small” data to apply to a larger population. (Remainder of
the book)
Basic Concepts
Variables, Values, and Scores:
A group of students answered the question, “How stressed have you been in the last 2.5 weeks?” on a scale of 0-
10, with 0 being not stressed at all and 10 being as stressed as possible.
Variable – a condition or characteristic that can have different values “level of stress”
Ex: height, social class, type of psychotherapy a patient receives, # of people absent from work
Value – possible number or category that a score can have “from 0-10”
Ex: any number like 4, -62, 72.15 or a category such as male or female or a medical diagnosis
Score – particular person’s value on a variable If I selected 6 as my answer, “6” would be the score.
Each person has a particular number or SCORE that is his or her value on the variable. Your score on the
stress test above may have been 6; another’s may have been 2.
Levels of Measurement (Kinds of Variables):
Types of underlying numerical information provided by a measure, such as equal-interval, rank-
order, and nominal (categorical)
1. Numeric variable – variable whose values are NUMBERS; in the stress ratings example, the higher the number
is, the more stress there is; aka quantitative variable
a. Equal-interval variable – variable in which the numbers stand for approximately equal amounts of
what is being measured; the difference between a 2.5 and a 2.8 GPA is the same as the difference
between a 3.0 and a 3.3 GPA
b. Rank-order variable – numeric variable in which the values are ranks, such as class standing or place
finished in a race; aka ordinal variable; the amount of difference in underlying GPA between being 2 nd
rd th th
and 3 in class may not be the same as the different between 8 and 9 in class. Provides less info
than an equal-interval variable.
2. Nominal variable – variable with values that are categories (i.e., they’re names, not numbers); aka categorical
variable; it is called nominal because the values are names and categorical because their values are categories;
for the nominal variable gender, the values are female and male and the scores are one of the two values. Chapter 1 – Displaying the Order in a Group of Numbers Using Tables and Graphs
Continuous
Discrete vs.
variable
variable
A variable with specific values and that can’t A variable in which there can be ∞ # of
have values between those specific values. values between any two values.
Ex: You can go to a dentist 2 times a Ex: You can be 20 years old or
year but you cannot go 2.72 20.56 years old.
Checkpoint:
1. A father rates his daughter as a 2 on a 7-point scale (17) of crankiness.
a. What is the variable? Crankiness
b. What is the score? 2
c. What is the range of values? 1-7
2. What is the difference between a numeric and a nominal variable?
A numeric variable has numbers as values that tell you the extent of what the variable measures, while a
nominal variable can include categories or names with no particular numerical order.
3. What is the difference between a discrete and a continuous variable?
A discrete variable is concrete. The values cannot have other values in between them. A continuous
variable can theoretically have an infinite number of values in between them.
Frequency Tables
Frequency table – ordered listing of number of individuals having each of the different values for a particular
variable.
Numeric Variables Frequency Table:
X-Value (Test score) Frequency (# of students)
0 2
1 5
2 7
3 8
4 11
5 7
6 3
7 1 Chapter 1 – Displaying the Order in a Group of Numbers Using Tables and Graphs
Nominal Variables Frequency Table:
94 students kept a diary of their social interactions for a week during the semester. Each time a student had an
interaction lasting 10+ minutes, they would fill out a card with questions about aspects of the conversation and the
conversation partner. The numbers of interactions lasting 10+ minutes over a week were as follows:
48, 15, 33, 3, 21, 19, 17, 16, 44, 25, 30, 3, 5, 9, 35, 32, 26, 13, 14, 14, 47, 47, 18, 11, 5, 19, 24, 17, 6, 25, 8, 18, 29, 1, 18, 22, 3, 22,
29, 2, 6, 10, 29, 10, 29, 21, 38, 41, 16, 17, 8, 40, 8, 10, 18, 7, 4, 4, 8, 11, 3, 23, 10, 19, 21, 13, 12, 10, 4, 17, 11, 21, 9, 8, 7, 5, 3, 22,
14, 25, 4, 11, 10, 18, 1, 28, 27, 19, 24, 35, 9, 30, 8, 26
1. Make a list down the page for each possible value, from lowest to highest. 0-48 for this example.
2. Going one-by-one through the scores, tally up how many scores there are per value.
3. Make a table showing how many times each value on the list was used.
4. Calculate the percentage of scores for each value.
Frequency Table for Number of Social Interactions During a Week for 94 College Students
Score Frequency Score Frequency Score Frequency
0 0 17 3 34 0
1 2 18 4 35 2
2 1 19 3 36 0
3 5 20 0 37 0
4 4 21 4 38 1
5 3 22 3 39 0
6 2 23 1 40 1
7 2 24 2 41 1
8 6 25 3 42 0
9

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