Types of Data
Qualitative data: consist of attributes,
labels, non-numerical values
(examples: hair color, political party, zip
code, favorite pizza)
Quantitative data: consist of numerical
measurements or counts (age, length of
forearm, number of Facebook friends)
Examples
Qualitative? Quantitative?
-
salaries of teachers
marital status of graduate students
social security numbers
number of cars in household
color of family car
Qualitative? Quantitative?
- salaries of teachers (quantitative)
- marital status of graduate students
(qualitative)
- social security numbers (qualitative)
- number of cars in household (quantitative)
- age of cars in household (quantitative)
- color of family car (qualitative)
Qualitative? Quantitative?
City
Baltimore
Jacksonville
Memphis
Pasadena
San Antonio
Seattle
Population
636,919
807,815
669,651
143,080
1,351,305
598,541
Levels of Measurement
Nominal : qualitative only. Data are
categorized using names, labels, or qualities.
No mathematical computations. (names of
baseball teams, social security numbers)
Ordinal: qualitative or quantitative. Data are
ordered or ranked, but differences between
data are not meaningful (final standings of NFC
West conference football teams)
Levels of Measurement
Interval : can be ordered; meaningful
differences between data values. However a
“zero” value does not imply absence of the
attribute (temperature) – [no inherent zero]
Ratio: like interval data, but also:
- “zero” value means absence of attribute
[inherent zero] (e.g. wind speed)
- one data value can be expressed as a
multiple of another (i.e., as a ratio)
(a dog weighing 20 pounds is twice as
heavy as a dog weighing 10 pounds)
Example
The following items appear on an employment
application. Identify the level of measurement for
each.
- highest previous salary
- gender
- year of college graduation
- number of years at last job
Example
The following items appear on an employment
application. Identify the level of measurement for each.
- highest previous salary (ratio; quantitative, makes
sense that $45000/yr is three times $15000/yr)
- gender (nominal)
- year of college graduation (interval; makes sense to
say that 2010 is 5 years later than 2005)
- number of years at last job (ratio)
A sports writer plans to list the winning times for
all the swimming events in the 2012 Olympics.
The writer wants to simply
organize the data and compile a
list (describe!) the medal winners
of the Olympics
descriptive study
A survey conducted among 1017 men and women
found that 76% of women and 60% of men had a
physical examination with the previous year.
Inferential? Descriptive? Both!
76% women, 60% men  Descriptive (simply describes
the data sample which was collected)
More women than men will have physical exams during
the year  Inferential (use the data sample to say
something about the population)