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Types of Variables AP Statistics 06-07Dobson

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

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

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

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Caution!!! Most quantitative variables can be asked in such a way as to make them a categorical variable. Most quantitative variables can be asked in such a way as to make them a categorical variable. Ex: Age: Ex: Age: Please choose the category that describes how old you are Please choose the category that describes how old you are 0-1920-39 40-59 60-79 OVER 80 0-1920-39 40-59 60-79 OVER 80

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

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

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

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