Slides: What is Data?
WHAT IS DATA?
ST101 – DR. ARIC LABARR
WHAT IS/ARE DATA?
data
noun
\ˈdā - tə\
factual information used as a basis for reasoning, discussion, or calculation
WHAT IS/ARE DATA?
data
noun
\ˈdā - tə\
factual information used as a basis for reasoning, discussion, or calculation
Information – measurements or values describing an object, person, place, thing, etc.
Examples:
Person – height, weight, age, race, spending habits, etc.
Car – mileage, gas mileage, color, motor size, etc.
Website – # of clicks, page views, ad revenue, etc.
WHAT IS/ARE DATA?
data
noun
\ˈdā - tə\
factual information used as a basis for reasoning, discussion, or calculation
Inference – using information to come to some conclusion.
Want to use the information to draw conclusions and make better decisions in the context of our problem.
Who, what, where, when, why, how?
DATA TABLE
Date
Weekday
Season
Weather Type
Temperature
(°F)
Humidity
(%)
# Casual Users
# Registered Users
1/1/2011
Saturday
Winter
Misty
46.7
80.6
331
654
1/2/2011
Sunday
Winter
Misty
48.4
69.6
131
670
1/3/2011
Monday
Winter
Clear /
Partly Cloudy
34.2
43.7
120
1229
1/4/2011
Tuesday
Winter
Clear /
Partly Cloudy
34.5
59.0
108
1454
1/5/2011
Wednesday
Winter
Clear /
Partly Cloudy
36.8
43.7
82
1518
…
DATA TABLE
…
Date
Weekday
Season
Weather Type
Temperature
(°F)
Humidity
(%)
# Casual Users
# Registered Users
1/1/2011
Saturday
Winter
Misty
46.7
80.6
331
654
1/2/2011
Sunday
Winter
Misty
48.4
69.6
131
670
1/3/2011
Monday
Winter
Clear /
Partly Cloudy
34.2
43.7
120
1229
1/4/2011
Tuesday
Winter
Clear /
Partly Cloudy
34.5
59.0
108
1454
1/5/2011
Wednesday
Winter
Clear /
Partly Cloudy
36.8
43.7
82
1518
Observations
DATA TABLE STRUCTURE
Rows in a data table typically denote observations.
Observations – individuals or objects that we are collected information about.
DATA TABLE
…
Date
Weekday
Season
Weather Type
Temperature
(°F)
Humidity
(%)
# Casual Users
# Registered Users
1/1/2011
Saturday
Winter
Misty
46.7
80.6
331
654
1/2/2011
Sunday
Winter
Misty
48.4
69.6
131
670
1/3/2011
Monday
Winter
Clear /
Partly Cloudy
34.2
43.7
120
1229
1/4/2011
Tuesday
Winter
Clear /
Partly Cloudy
34.5
59.0
108
1454
1/5/2011
Wednesday
Winter
Clear /
Partly Cloudy
36.8
43.7
82
1518
Variables
DATA TABLE STRUCTURE
Rows in a data table typically denote observations.
Observations – individuals or objects that we are collected information about.
Columns in a data table typically denote variables.
Variables – different characteristics that describe the observations.
TYPES OF VARIABLES
There are two main types of variables:
Qualitative
Quantitative
TYPES OF VARIABLES
There are two main types of variables:
Qualitative – data with a measurement scale inherently categorical.
Quantitative
QUALITATIVE (CATEGORICAL) VARIABLES
…
Date
Weekday
Season
Weather Type
Temperature
(°F)
Humidity
(%)
# Casual Users
# Registered Users
1/1/2011
Saturday
Winter
Misty
46.7
80.6
331
654
1/2/2011
Sunday
Winter
Misty
48.4
69.6
131
670
1/3/2011
Monday
Winter
Clear /
Partly Cloudy
34.2
43.7
120
1229
1/4/2011
Tuesday
Winter
Clear /
Partly Cloudy
34.5
59.0
108
1454
1/5/2011
Wednesday
Winter
Clear /
Partly Cloudy
36.8
43.7
82
1518
TYPES OF VARIABLES
There are two main types of variables:
Qualitative – data with a measurement scale inherently categorical.
Nominal – categories with no logical ordering.
Ordinal – categories with a logical ordering.
Quantitative
QUALITATIVE (CATEGORICAL) VARIABLES
…
Date
Weekday
Season
Weather Type
Temperature
(°F)
Humidity
(%)
# Casual Users
# Registered Users
1/1/2011
Saturday
Winter
Misty
46.7
80.6
331
654
1/2/2011
Sunday
Winter
Misty
48.4
69.6
131
670
1/3/2011
Monday
Winter
Clear /
Partly Cloudy
34.2
43.7
120
1229
1/4/2011
Tuesday
Winter
Clear /
Partly Cloudy
34.5
59.0
108
1454
1/5/2011
Wednesday
Winter
Clear /
Partly Cloudy
36.8
43.7
82
1518
TYPES OF VARIABLES
There are two main types of variables:
Qualitative – data with a measurement scale inherently categorical.
Nominal – categories with no logical ordering.
Ordinal – categories with a logical ordering.
Quantitative – data that are numeric and define a value or quantity.
QUANTITATIVE (NUMERICAL) VARIABLES
…
Date
Weekday
Season
Weather Type
Temperature
(°F)
Humidity
(%)
# Casual Users
# Registered Users
1/1/2011
Saturday
Winter
Misty
46.7
80.6
331
654
1/2/2011
Sunday
Winter
Misty
48.4
69.6
131
670
1/3/2011
Monday
Winter
Clear /
Partly Cloudy
34.2
43.7
120
1229
1/4/2011
Tuesday
Winter
Clear /
Partly Cloudy
34.5
59.0
108
1454
1/5/2011
Wednesday
Winter
Clear /
Partly Cloudy
36.8
43.7
82
1518
TYPES OF VARIABLES
There are two main types of variables:
Qualitative – data with a measurement scale inherently categorical.
Nominal – categories with no logical ordering.
Ordinal – categories with a logical ordering.
Quantitative – data that are numeric and define a value or quantity.
Not all variables that are numeric are quantitative.
Examples – date, SSN, ZIP code, etc.
Need to be able to do basic arithmetic and remain meaningful.
QUANTITATIVE (NUMERICAL) VARIABLES
…
Date
Weekday
Season
Weather Type
Temperature
(°F)
Humidity
(%)
# Casual Users
# Registered Users
1/1/2011
Saturday
Winter
Misty
46.7
80.6
331
654
1/2/2011
Sunday
Winter
Misty
48.4
69.6
131
670
1/3/2011
Monday
Winter
Clear /
Partly Cloudy
34.2
43.7
120
1229
1/4/2011
Tuesday
Winter
Clear /
Partly Cloudy
34.5
59.0
108
1454
1/5/2011
Wednesday
Winter
Clear /
Partly Cloudy
36.8
43.7
82
1518
SUMMARY
Data – factual information used as a basis for reasoning, discussion, or calculation.
Data typically structured with data tables.
Rows – observations.
Columns – variables.
Types of variables:
Qualitative – categorical.
Quantitative – numerical.
EXPLORING RELATIONSHIPS WITH DATA
WHAT IS DATA?
DATA INTO INSIGHTS
Data by itself is just information.
Need to draw insights from data to make decisions.
Insights come from exploring your data.
EXAMPLE – BIKE RENTAL DATA
Date
Weekday
Season
Weather Type
Temperature
(°F)
Humidity
(%)
# Casual Users
# Registered Users
1/1/2011
Saturday
Winter
Misty
46.7
80.6
331
654
1/2/2011
Sunday
Winter
Misty
48.4
69.6
131
670
1/3/2011
Monday
Winter
Clear /
Partly Cloudy
34.2
43.7
120
1229
1/4/2011
Tuesday
Winter
Clear /
Partly Cloudy
34.5
59.0
108
1454
1/5/2011
Wednesday
Winter
Clear /
Partly Cloudy
36.8
43.7
82
1518
…
EXAMPLE – BIKE RENTAL DATA
Historical average bike rentals is 4,000 per day.
New employee sees low bike rental numbers over the first few days of the new year.
Trouble?
EXAMPLE – BIKE RENTAL DATA
EXAMPLE – BIKE RENTAL DATA
Historical average bike rentals is 4,000 per day.
New employee sees low bike rental numbers over the first few days of the new year.
Trouble? – Can look at the distribution of daily bike rentals.
EXAMPLE – BIKE RENTAL DATA
Historical average bike rentals is 4,000 per day.
New employee sees low bike rental numbers over the first few days of the new year.
Maybe bike rentals drop in the winter?
EXAMPLE – BIKE RENTAL DATA
EXAMPLE – BIKE RENTAL DATA
Historical average bike rentals is 4,000 per day.
New employee sees low bike rental numbers over the first few days of the new year.
Maybe bike rentals drop in the winter?
Can look at a bar chart of the data to see possible association.
EXAMPLE – BIKE RENTAL DATA
Historical average bike rentals is 4,000 per day.
New employee sees low bike rental numbers over the first few days of the new year.
Very intriguing!
Is the drop in winter the same for registered and casual users?
EXAMPLE – BIKE RENTAL DATA
EXAMPLE – BIKE RENTAL DATA
Historical average bike rentals is 4,000 per day.
New employee sees low bike rental numbers over the first few days of the new year.
Very intriguing!
Is the drop in winter the same for registered and casual users?
Can look at stacked bar chart to see how users break down into registered and casual users.
EXAMPLE – BIKE RENTAL DATA
Very intriguing!
Tons of things revealed by data.
Why do customers use bike rentals less in winter? Temperature?
EXAMPLE – BIKE RENTAL DATA
EXAMPLE – BIKE RENTAL DATA
Very intriguing!
Tons of things revealed by data.
Why do customers use bike rentals less in winter? Temperature?
Can look at scatterplot of temperature and user count to see possible relationship.
EXAMPLE – BIKE RENTAL DATA
Very intriguing!
Tons of things revealed by data.
Why do customers use bike rentals less in winter? Temperature?
Can look at scatterplot of temperature and user count to see possible relationship.
What about registered or casual users?
EXAMPLE – BIKE RENTAL DATA
EXAMPLE – BIKE RENTAL DATA
SUMMARY
Data by itself is just information.
Exploring data reveals potential insights and valuable uses of that information.
Visuals help explore data.
Distributions, bar charts, stacked bar charts, scatterplots, etc.
ASSOCIATION AND CORRELATION
WHAT IS DATA?
EXPLORING DATA RELATIONSHIPS
Exploring data reveals potential insights and valuable uses of that information.
Visuals help explore data.
Distributions, bar charts, stacked bar charts, scatterplots, etc.
Are visuals enough?
EXAMPLE – BIKE RENTAL DATA
EXAMPLE – BIKE RENTAL DATA
EXAMPLE – BIKE RENTAL DATA
Average of each
Season
EXAMPLE – BIKE RENTAL DATA
Range of each
Season
VARIATION
One of the most important concepts in statistics is variation.
Data points vary from one to another and that is expected:
Don’t see everything.
Measure things imperfectly.
VARIATION
Why does one day in summer different than another? What if temperature is the same?
Can’t be perfectly sure why days are different.
Differences are expected by apparent randomness.
Are the seasons truly different? Or could there be some expected random variation?
EXAMPLE – BIKE RENTAL DATA
STATISTICAL TESTING
Statistical hypothesis testing can help answer these questions.
Use the data available to see if the differences we see are expected due to just random variations or if we can say there is an association between season and number of users.
An association is a statistical relationship between a qualitative and quantitative variable.
STATISTICAL TESTING USEFULNESS
Examples:
Did the previous marketing campaign bring in more customers?
Did that drug treatment help the patient?
Did our program for veterans help them find jobs after they left the service?
EXAMPLE – BIKE RENTAL DATA
EXAMPLE – BIKE RENTAL DATA
75°F has values
ranging from
1,000 – 8,000
STATISTICAL CORRELATION
Variation occurs when looking for relationships between two quantitative variables as well.
Use the data available to see if the differences we see are expected due to just random variations or if we can say there is a correlation between temperature and number of users.
A correlation is a statistical linear relationship between two quantitative variables.
Stronger the correlation 🡪 stronger the linear relationship.
SUMMARY
Data has natural and expected variation.
Some of this variation could be due to apparent randomness.
Statistical testing can help evaluate if the variation is random or intentional.
An association is a statistical relationship between a qualitative and quantitative variable.
A correlation is a statistical linear relationship between two quantitative variables.
DATA IN THE WORLD AROUND US
WHAT IS DATA?
WORLDWIDE DATA PRODUCTION
Data is everywhere.
1 zettabyte = 1,000,000,000,000 GB
If you were to fill the latest smart phone full of data… stacked them end to end… they would go to the moon… and back to Earth… and back to the moon again!
*IDC Digital Universe
DATA IS EVERYWHERE
Data exists in all types of industries – only depends on how it is used!
Banking / Finance
Marketing
Healthcare
Supply Chain / Agriculture
BANKING / FINANCE
Who do banks give loans to?
Microfinance banks help impoverished and developing nations through small business loans.
Use data modeling to help find which clients would be best to loan money to at the least risk.
$
$
$
$
$
$
?
?
MARKETING
Who do you advertise to?
How do you advertise to them?
Marketing companies use statistical hypothesis tests to compare effectiveness of different campaigns.
Data about customer purchases helps companies group customers into similar buying habits.
Social influencer vector created by storyset - www.freepik.com
HEALTHCARE
Healthcare costs are increasing.
How can we make healthcare more efficient without losing quality of care?
Hospitals and medical agencies use data to help identify onset of disease sooner, determine who is at higher risk for hospital readmission, and provide more specialized care for patients.
Health data vector created by katemangostar - www.freepik.com
SUPPLY CHAIN / AGRICULTURE
How do we use food more efficiently?
Agriculture companies use data to efficiently track food from their seed, to the field, to the store, and to the table.
This helps keep food fresher longer.
SUMMARY
Data exists in all types of industries – only depends on how it is used!
Knowledge of data and its usefulness is helpful in all aspects of life, not just in the career you are going.
Last modified: Monday, October 17, 2022, 12:51 PM