Types of Variables

# Types of Variables

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## Types of Variables

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1. Types of Variables AP Statistics 06-07 Dobson

2. Review of Terms • Individual: The objects described by a set of data, individuals may be people, animals or things • Ex: Students in an AP Statistics class • Variable: any characteristic of an individual. A variable can take on different values for different individuals • Ex: Heights of individuals: Student #1: 5’ 5” Student #2: 5’ 7” Student #3: 5’ 2”

3. Two Types of Variables • Quantitative: • Numeric value that it makes sense to do arithmetic operations (+, -, x, /) • Finding an arithmetic “average” makes sense • EX: • Height • Weight • Age • Income • Test Scores

4. Types of Variables • Categorical • Records which of several groups or categories to which an individual belongs • If there are only 2 possible categories, the variable is called binary • Ex: • Gender • Race • SES (socio-economic status) • Marital status

5. Caution!!! • Most quantitative variables can be asked in such a way as to make them a categorical variable. • Ex: Age: • Please choose the category that describes how old you are • 0-19 20-39 40-59 60-79 OVER 80

6. Determine if the variable isQuantitative or Categorical • Height • Armspan • Whether or not the individual went to sleep before 12:00am • Month of birth • Distance from home • Whether the individual has a cell phone • How many e-mail messages a person has sent in the last 24 hours • The age of a bride on her wedding day • Whether the bride is older, younger, or the same age as the groom in a wedding couple • The number of letters in a person’s last name Check your answers on the next slide

7. Quantitative Variables • Height • Armspan • Distance from home • How many e-mail messages a person has sent in the last 24 hours • The age of a bride on her wedding day • The number of letters in a person’s last name Categorical • Whether or not the individual went to sleep before 12:00am • Month of birth • Whether the individual has a cell phone • Whether the bride is older, younger, or the same age as the groom in a wedding couple

8. Further Resources • Practice of Statistics: pg 4-7 • Homework Assignment: • 1-1: Problem #1a-p