### slides from class 1

```ISQS 5345-002 STATISTICAL
CONCEPTS FOR
MANAGEMENT
What is
Statistics?
A way of
*
understanding data.
* Not the way.
What is
Data?
The Understanding Process
Transform
Why study
statistics?
To Summarize
• Stat is A way of understanding data
• Data is anything perceivable
• Data is converted to information for
understanding
• Stat is a language of business
• Stat is a series of if…then statements
• Human brains do not naturally think
statistically
Elementary
Units
Variable
Thing
Attributes
Age
Height
Income
Hair Color
Favorite Food
Values
25 Years
1.5 M
\$40,000
Brown
Cheesecake
Elementary
Units
Variable
Thing
Attributes
Age
Height
Income
Hair Color
Favorite Food
Values
45Years
1.7 M
\$70,000
Gray
Cheesecake
Elementary
Units
Variable
Thing
Attributes
Age
Height
Income
Hair Color
Favorite Food
Values
25Years
1.5 M
\$40,000
Brown
Cheesecake
A dataset is a
collection of values
of attributes of many
things
How Many Variables?
• Univariate data set: One variable measured for
each elementary unit
– e.g., Sales for the top 30 computer companies.
– Can do: Typical summary, diversity, special features
• Bivariate data set: Two variables
– e.g., Sales and # Employees for top 30 computer firms
– Can also do: relationship, prediction
• Multivariate data set: Three or more variables
– e.g., Sales, # Employees, Inventories, Profits, …
– Can also do: predict one from all other variables
Irwin/McGraw-Hill
Numbers or Categories?
• Quantitative Variable: Meaningful numbers
– e.g., Sales, # Employees
• Qualitative Variable: Categories
– Ordinal Variable: Categories with meaningful ordering
• e.g., Bond rating (AA, A, B, …), Diamonds (VSI, SI, …)
• Can rank, count
– Nominal Variable: categories without meaningful
ordering
• e.g., State, Type of business, Field of study
• Can count
Irwin/McGraw-Hill
Time-Series or Cross-Sectional?
• Time-Series Data: Data values recorded in
meaningful sequence
– Elementary units might be days or quarters or years
– e.g., Daily Dow-Jones stock market average close for
the past 90 days
– e.g., Your firm’s quarterly sales over the past 5 years
• Cross-Sectional Data: No meaningful sequence
– e.g., Sales of 30 companies
– e.g., Productivity of each sales division
– Easier than time series!
Irwin/McGraw-Hill
Example
Firm
Sales
Industry Group
IBM
66,346
Office Equipment
A
Exxon
59,023
Fuel
A-
GE
40,482
Conglomerates
A+
AT&T
34,357
Telecommunications
A-
Irwin/McGraw-Hill
S&P Rating
Example (continued)
Multivariate Data (3 variables)
Firm
Sales
Industry Group
IBM
66,346
Office Equipment
A
Exxon
59,023
Fuel
A-
GE
40,482
Conglomerates
A+
AT&T
34,357
Telecommunications
A-
Elementary
units
Irwin/McGraw-Hill
Quantitative
variable
Nominal
Qualitative
variable
S&P Rating
Ordinal
Qualitative
variable
Example
Year
1995
1996
1997
1998
1999
2000
Irwin/McGraw-Hill
Budget (\$ Millions)
677
873
333
-77
57
287
Example
Year
1995
1996
1997
1998
1999
2000
Elementary unit
defined by “year”
Irwin/McGraw-Hill
Budget (\$ Millions)
677
873
333
-77
57
287
Quantitative data
Stock Market – Time Series
• S&P Stock Index, monthly since 1925
1,600
S&P stock market index
1,400
1,200
1,000
800
600
400
200
0
1920
1930
1940
1950
1960
Year
Irwin/McGraw-Hill
1970
1980
1990
2000
Sources of Data
• Primary Data
• When you control the design and data collection
• Production data from your factory