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