Chapter 2: Types of Data and Displays
Collected data may be classified into one of
two broad categories:
1. Qualitative data – consists of
observations which can be placed into
categories. The categories describe
some attribute or quality of interest.
Examples: College Major
Favorite Color
Political Party Preference
Chapter 2: Types of Data and Displays
(Continued)
2. Quantitative data – consists of
observations that measure some
quantity of interest. Each observation is
a number.
Examples:
College GPA
Number of Emergency Room Patients
Price of gasoline in the area
Chapter 2: Quantitative vs Qualitative Data
It is tempting to say numbers represent
quantitative data, while words represent
qualitative data.
What does the “205” represent in STA 205?
Does it really mean it is a harder course
than all MAT/STA courses with lower
numbers?
This is a scheme to categorize MAT/STA
classes. It does nothing except categorize
the course. It does not measure
anything, right?
Self-Quiz for Practice
Classify each set of data as either
quantitative or qualitative data:
1. The heights of current STA 205 students
2. The GPAs of current STA 205 students
3. The favorite ice cream flavors of all U.S.
senators
4. The home telephone numbers for all
players on the Cincinnati Reds baseball
team
5. Gas mileages for the cars parked next
to this building
Answers to Self-Quiz
1.
2.
3.
4.
5.
heights - Quantitative
GPAs - Quantitative
ice cream flavors - Qualitative
telephone numbers - Qualitative
Gas mileages – Quantitative
Notice in 1, 2, and 5 the numbers obtained
measure something. Although # 4
gives a “number”, it locates a place but
does not measure anything.
Brief Comments
Presenting and Analyzing the two types of
data require different techniques.
Most of the discussion in this class focuses
on quantitative data. However, we will
mention techniques of inference for
qualitative data also (proportions, chisquare test of contingency tables)