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Stats: Modeling the
World
Chapter 1: Introductory vocabulary and Concepts
Statistics is about variation:
When we take measurements in an experiment we expect individuals to be slightly different. Statistics helps to explain that variability between individuals:
How much difference is simply due to random variation?
-For example: Person A and Person B just coincidently have the same response.
When is a difference so large that something other than random variation is at work?
-For example: Trends within population do all younger people tend to choose one option while older people tend to choose another option.
How to Approach a Stats Problem
•Think: Know where you’re headed and why
•Show: is about the mechanics of calculating statistics and making graphical displays.
•Tell: Explain your results so that someone else can understand your conclusion.
Data in Statistics
• Statistics helps us to make sense of the world described
by our data by seeing past the underlying variation to find
patterns and relationships.
• Data: any collection of numbers, characters, images,
or other information that provide information about
something.
Try to Guess what they represent:
? ? ?
D. Brittany Y 5
S. Deborah N 2
M.Steven Y 3
The values in the data table
meaningless without
context. Context ideally
tells who and what was
measured.
Data Table: Clearly
shows the context of
data presented
The “W’s”
To provide context we need the W’s:
• Who
• What ( and in what units)
• When
• Where
• Why (if possible)
• And How
Of the data
The Who
• Who: the individual for which who ( or whom) we have collected data
Names(Who) ? ?
D. Brittany Y 5
S. Deborah N 2
M.Steven Y 3
What & Why
• What: Are characteristics recorded about each individual
Names(Who) Gifts
(What & Why)
#Gifts (What &
Why)
D. Brittany Y 5
S. Deborah N 2
M.Steven Y 3
Categorical & Quantitative Variables
Ask yourself how you would answer that
• Categorical: Variable
with category response
• Class Examples??
• Quantitative: Variable
with numerical
response
• Class Examples??
Can you identify the variable type?
• A medical researcher measures the
increase in heart rate of patients
under a stress test. What kind of
variable is the researcher studying?
• Heart rate is a numerical
measurement. Therefore he is
measuring a quantitative variable.
Why do we differentiate Category &
Quantitative
• The questions we ask a variable shape what we think about and how we treat
the variable.
• The analysis done on a categorical variables and quantitative variables differs.
• THINK , SHOW , TELL: so think and show will look different depending
on which type of variable you have.
• Learn to identify the two types
Categorical Variables
• We usually use a frequency table for categorical variables.
• For example, here is a frequency table for the question, “What shipping
method was chosen?”
Shipping Method (Variable) # of Purchases
Ground 20,345
Second-Day 7,780
Overnight 5,432
Frequency Counts for
each category
Response
level(choice)
for categorical
variable
Using Frequency Counts
• When we focus on the amount of
something (frequency) we use
counts differently.
• For example, Amazon might track
the growth in the number of
teenage customers each much to
predict CD sales for the next year.
Month # Teen
Customers
January 123,000
February 234,000
March 345,678
Using Frequency Counts
. Month # Teen
Customers
January 123,000
February 234,000
March 345,678
The Who is months and the units are
the number of Teens
Amazon is interested in the months
The What is teens
Amazon describes the months by
number of teens
Identify the Who and What: Ex.Blind
• A study began in 2011 examines the use of stem cells in treating two forms
of blindness. Stargardt’s disease, and dry age-related macular degeneration.
Each of the 24 patients entered one of two separate trials in which
embryonic stem cells were to be used to treat the condition.
• Who are we interested in?
• What do we want to know about the patient?
• What do we want to know about the treatment?
Identify the Who and What:Ex.Blind
• A study began in 2011 examines the use of stem cells in treating two forms of blindness. Stargardt’s disease, and dry age-related macular degeneration. Each of the 24 patients entered one of two separate trials in which embryonic stem cells were to be used to treat the condition.
• Who are we interested in? 24 patients entered into the two trials
• What do we want to know about the patient? Whether the patient has Stargardt’s disease or Macular Degeneration?
• What do we want to know about the treatment? Whether the tem cell treatment was effective or not
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