COURSE: JUST 3900
INTRODUCTORY STATISTICS
FOR CRIMINAL JUSTICE
Chapter 1: Introduction to Statistics
Peer Tutor Slides
Instructor:
Mr. Ethan W. Cooper, Lead Tutor
© 2013 - - PLEASE DO NOT CITE, QUOTE, OR REPRODUCE WITHOUT THE
WRITTEN PERMISSION OF THE AUTHOR. FOR PERMISSION OR QUESTIONS,
PLEASE EMAIL MR. COOPER AT THE FOLLWING: coopere07@students.ecu.edu
Learning statistics is like learning a
foreign language: Make notecards to
help you learn your key terms
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Population (p. 5)
Sample (p. 6)
Variable (p. 6)
Parameter (p. 7)
Statistic (p. 7)
Descriptive Statistics (p. 8)
Inferential Statistics (p. 9)
Correlational Method (p. 13)
Experimental Method (p.16)
More Key Terms: Think Notecards
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Independent Variable (p. 16)
Dependent Variable (p. 16)
Control Condition (p. 16)
Experimental Condition (p. 16)
Nonexperimental Studies (p. 17)
Quasi-independent Variable (p. 18)
Constructs (p. 20)
Operational Definition (p. 20)
More Key Terms: Think Notecards
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Discrete Variable (p. 21)
Continuous Variable (p. 21)
Real limits (p. 22)
Nominal Scale (p. 23)
Ordinal Scale (p. 23)
Interval Scale (p. 25)
Ratio Scale (p. 25)
Order of Operations (p. 27)
Statistics, Population, and
Samples
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Question1: If a researcher measures the number of text
messages that each individual high school student sends
each day and calculates the average number for the entire
group of high school students, the average number would be
an example of a ________.
Statistics, Population, and
Samples
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Question 1 Answer: Parameter. The researcher uses the
entire population of college students.
Statistics, Population, and
Samples
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Question 2: A researcher is interested in how watching a
reality TV show featuring fashion models influences the
eating behavior of 13-year-old girls.
a)
b)
A group of 30 13-year-old girls is selected to participate in a
research study. The group of 30 13-year-old girls is an example
of a ________.
In the same study, the amount of food eaten in one day is
measured for each girl and the researcher computes the
average score for the 30 13-year-old girls. The average score is
an example of a _________.
Statistics, Population, and
Samples
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Question 2 Answers:
a)
b)
Sample
Statistic
Research Methods
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Question 3: Researchers have observed that high school
students who watched educational television programs
as young children tend to have higher grades than their
peers who did not watch educational television. Is this
study an example of an experiment? Why or why not?
Research Methods
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Question 3: Answer: This study could be correlational or
nonexperimental, but it is definitely not an example of a
true experiment. The researcher is simply observing, not
manipulating, the amount of educational television.
Research Methods
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Question 4: What two elements are necessary for a
research study to be an experiment?
Research Methods
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Question 4 Answer: First, the researcher must
manipulate one of the two variables being studied.
Second, all other variables that might influence the
results must be controlled.
Research Methods
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Question 5: Loftus and Palmer (1974) conducted an
experiment in which participants were shown a video of
an automobile accident. After the video, some
participants were asked to estimate the speed of the
cars when they “smashed into” each other. Others were
asked to estimate the speed when the cars “hit” each
other. The “smashed into” group produced significantly
higher estimates than the “hit” group. Identify the
independent and dependent variables for this study.
Research Methods
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Question 5 Answer: The independent variable is the
phrasing of the question and the dependent variable is
the speed estimated by each participant.
Variables and Measurement
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Question 6: A survey asks people to identify their age,
annual income, and marital status (single, married,
divorced, etc.). For each of these three variables, identify
the scale of measurement that is used and identify
whether the variable is continuous or discrete.
Variables and Measurement
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Question 6 Answer: Age and annual income are
measured on ratio scales and are both continuous
variables. Marital status is measured on a nominal scale
and is a discrete variable.
Variables and Measurement
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Question 7: An English professor uses letter grades (A,
B, C, D, and F) to evaluate a set of student essays. What
kind of scale is being used to measure the quality of the
essays?
Variables and Measurement
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Question 7 Answer: Ordinal
Variables and Measurement
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Question 8: The teacher in a communications class asks
students to identify their favorite reality television show.
The different television shows make up what kind of
scale?
Variables and Measurement
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Question 8 Answer: Nominal
Variables and Measurement
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Question 9: When measuring height to the nearest inch,
what are the real limits for a value of 68 inches?
Variables and Measurement
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Question 9 Answer: 67.5 and 68.5
67
68
67.5
69
68.5
Variables and Measurement
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Question 10: When measuring height to the nearest half
inch, what are the real limits for a value of 68 inches?
Variables and Measurement
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Question 10 Answer: 67.75 and 68.25
67.5
68
67.75
68.5
68.25
Discrete or Continuous?
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Question 11:
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Foot length
Height
Time
Number of students in JUST 3900
Weight
Number of siblings
Age
Discrete or Continuous?
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Question 11 Answer:
Foot length, height, weight, age, and time are all
continuous because they are not limited to a fixed set of
separate, individual categories. They can be divided into
an infinite number of fractional parts. It is always
possible to find a third point between any two points.
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Height and foot length, for instance, can be measured in meters,
centimeters, and even millimeters.
Time and age can be broken down into years, months, days,
hours, seconds, or milliseconds.
When two people say they each weigh 150 lbs., what they likely
mean is that they each weigh about 150 lbs. There are an
infinite number of possibilities between 149 lbs. and 150 lbs. and
150 lbs. and 151 lbs. that would more accurately describe their
respective weights.
Discrete or Continuous?
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Question 11 Answer:
The number of students enrolled in JUST 3900 and the
number of siblings one has are both discrete variables.
They consist of separate, indivisible categories.
Typically, discrete variables consist of whole, countable
numbers. No values exist in between.
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For instance, there may be 100 students enrolled in JUST 3900
or one may have 7 siblings, but there cannot be 99.5 students or
7.5 siblings.
Order of Operations
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Parentheses
Exponents
Multiplication/Division (in order from left to right)
Summation
Addition/Subtraction (in order from left to right)
Order of Operations
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Question 12: Calculate each value requested for the
following scores: 6,2,4,2.
a)
b)
c)
d)
e)
ΣX
ΣX2
(ΣX)2
Σ(X-2)
Σ(X-2)2
Order of Operations
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Question 12 Answers:
a)
b)
c)
d)
e)
𝑋 = 6 + 2 + 4 + 2 = 14
𝑋 2 = 62 + 22 + 42 + 22 = 36 + 4 + 16 + 4 = 60
𝑋 2 = 6 + 2 + 4 + 2 2 = 142 = 196
𝑋−2 = 6−2 + 2−2 + 4−2 + 2−2 =
4+0+2+0=6
2
𝑋−2 = 6−2 2+ 2−2 2+ 4−2 2+ 2−2
42 + 02 + 22 + 02 = 16 + 0 + 4 + 0 = 20
2
=
Summation Notation
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Question 13: Use summation notation to express each of
the following.
a)
b)
c)
Add 4 points to each score and then add the resulting values.
Add the scores and then square the total.
Square each score, then add the squared values.
Summation Notation
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Question 13 Answers:
a)
b)
c)
𝑋+4
𝑋 2
𝑋
2
Frequently Asked Questions
FAQs
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How do I pass this class?
1)
2)
3)
4)
5)
6)
7)
8)
Read the chapters before lectures.
Complete Aplia tutorials/practice questions in preparation for
in-class exercises.
If needed finish in-class exercises at home.
Come to tutoring (Workshops and Day time appointments).
Review the answer key to the in-class exercises before
completing the graded portion of Aplia.
Never take a homework free holiday! (Towards the end of the
semester this will make more sense)
Finish Aplia within 24 hours of the last lecture!
Always bring slides to class and take notes.
Frequently Asked Questions
FAQs
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What should I expect on the tests?
a)
b)
c)
d)
Tests will consist of approximately 45 multiple choice
questions.
The final exam will consist of approximately 60 multiple choice
questions.
The material covered on the test will include knowledge of
concepts, definitions, and formulas (know your terms).
Strictly speaking, the tests are not cumulative. Each exam will
only cover 3 chapters.
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e)
However, statistics is a course that builds on the foundation that was laid in
past chapters. If you do not understand chapters 1-3, you will not grasp
chapters 4-6. “A small error in the beginning leads to a large error in the
end.” Aristotle
Any tables required for the test (e.g., the tables in the
textbook’s appendices) will be provided by Dr. Kerbs.
What is it Really Like to be a
JUST3900 Student?
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Taking JUST3900 with Dr. Kerbs: FACT OR FICTION
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Taking JUST3900 with Dr. Kerbs is a demanding experience. FACT
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Dr. Kerbs does expect a great deal from his students -- he wants you to understand
and preferably master the course material. However, he provides you with every
resource to excel in his class: PowerPoint slides, in-class exercises with a detailed
explanation of each problem, a great text book, office hours, and tutoring services.
He gives you the tools to succeed in understanding and applying course content.
That said, you need to do your part as well: Read before each class, attend each
class and take notes, review your notes between classes, complete all homework
assignments, ask questions, and study for each test.
Getting extra help is difficult. FICTION
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Dr. Kerbs is very approachable on all levels. First, he wants students to ask
questions in class and during office hours. If you’re asking questions, it means that
you are trying to learn the material: This is a good thing! You can always expect that
Dr. Kerbs will take your questions and requests for help seriously, and he will always
treat you with respect and courtesy. Second, he holds office hours every week and
is available by appointment. He is known for diligently helping students because he
really does want you to succeed.