2. 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

3. 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

4. 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?

5. 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

6. Answers to Self-Quiz 1.heights - Quantitative 2.GPAs - Quantitative 3.ice cream flavors - Qualitative 4.telephone numbers - Qualitative 5.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.

7. 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, chi- square test of contingency tables)