Identifying Individuals and Variables and Classifying Variables as Categorical or Quantitative
Video Follow-Along Worksheet
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Learning Objectives:
Identify the individuals and variables in a data set.
Recognize that a variable is a characteristic that changes from one individual to another.
Classify variables as categorical or quantitative.
Explain why some number-valued fields, such as zip code or grade level, are still categorical.
Describe how grouped quantitative values can be turned into categories.
Essential Knowledge:
Individuals are the people, animals, or objects described by the data.
A variable is a characteristic that changes from one individual to another.
A categorical variable takes on values that are category names or group labels.
A quantitative variable takes on numerical values for a measured or counted quantity.
Not every field with numbers is quantitative; some numbers act only as labels or identifiers.
Units matter when a quantitative variable is measuring something.
Key Vocabulary
Individual
A person, animal, or object described by the data.
Variable
A characteristic that changes or varies from one individual to another.
Identifier
A label, such as an ID number, used to name individuals rather than describe a varying characteristic.
Categorical Variable
A variable whose values are category names or group labels.
Quantitative Variable
A variable whose values are numbers representing a measured or counted quantity.
Measured Quantity
A numerical value found by measuring, such as distance or height.
Count
A numerical value found by counting, such as number of bedrooms.
Units
The measurement labels attached to a quantitative variable, such as miles or milliseconds.
Group Label
A word or name used to place an individual into a category.
Spreadsheet
A table in which rows often show individuals and columns often show variables.
Video 1: The Language of Variation: Variables
[0:00 – 8:24]
1.[0:20]
In this lesson, you learn how to identify the and in a data set.
2.[0:43]
In the Charleston example, the data are presented rather than graphically.
Charleston Home Prices Data Set[0:35 – 1:11]
The video uses a spreadsheet of home prices in Charleston, South Carolina. The rows represent properties for sale, and the columns represent characteristics recorded for each property.
3.[0:54]
The individuals in a data set can be , , or .
4.[1:03]
In this spreadsheet, the individuals are shown in the .
5.[1:08]
The individuals represent the for sale in Charleston, .
6.[1:17]
A variable is a that changes or from one individual to another.
7.[1:29]
In a spreadsheet, the variables are usually shown in the of the table.
8.[1:35]
The leftmost ID column is an , so it is not actually a .
Examples of Variables in the Charleston Data[1:51 – 2:28]
Type of property
Sales price
Year built
Number of bedrooms
Whether or not it has a pool
Distance to the beach in miles
Parking location
Zip code
9.[1:55]
Some variables in this data set are , , , and .
10.[2:17]
Instead of repeating the label "pool?", you should describe the variable as whether or not the property has a .
11.[2:43]
A categorical variable takes on values that are or .
12.[2:55]
In the Charleston data, categorical variables include whether or not it has a pool, , and .
13.[3:08]
Zip code uses numbers, but those numbers are really representing a .
14.[3:17]
A quantitative variable takes on for a .
15.[3:24]
One clue that a variable is quantitative is that it makes sense to find an of its values.
16.[3:34]
Quantitative variables in the data set include , , , and distance to the beach measured in .
17.[3:43]
When a variable measures something, you should always state the of measurement.
Tips for Classifying Variables[3:50 – 5:04]
The video points out that categorical data are the values of a categorical variable, quantitative data are the values of a quantitative variable, and some numerical-looking values are still categories. It also shows that a quantitative variable can be grouped into categories such as close, nearby, and far.
18.[4:27]
Not all variables that take numerical values are ; zip code is the example used in the video.
19.[4:37]
Researchers can turn a variable into a variable by grouping values together.
20.[4:46]
In the beach-distance example, the grouped labels were , , and .
Student Survey Practice[5:12 – 7:29]
Mr. Starnes then uses a survey of 30 AP Statistics students with items such as grade level, age, favorite season, birth month, reaction time in milliseconds, height in centimeters, whether students can roll their tongue, and the number of people in the household.
21.[6:08]
The number of students in the AP Statistics class is not a variable because it is a , and its value is .
22.[6:44]
In the survey, age is , while birth month is .
23.[7:07]
Grade level is still even though it may be coded with numbers.
24.[7:27]
Number of people living in a household is because it is a .
Topic 1.2 Takeaways[7:44 – 8:19]
Individuals are the people, animals, or objects described by the data.
A variable is a characteristic that changes from one individual to another.
Categorical variables use category names or labels.
Quantitative variables use numerical values for measured or counted quantities.
25.
Reflection: Using the Charleston spreadsheet, explain the difference between an individual and a variable.
26.
Reflection: Why are zip code and grade level considered categorical variables even though they can be written with numbers?
Exit Ticket
A school keeps a spreadsheet for 25 students who play a spring sport. The columns are student ID, sport played, resting heart rate in beats per minute, and number of practices missed this month.
(a) Identify the individuals in this data set.
(b) Name two variables from the spreadsheet and describe what each one measures or records.
(c) Classify sport played and resting heart rate as categorical or quantitative, and explain why.
(d) Explain why student ID would not count as a variable for this lesson, even though it appears in a column.
Class Responses (Esc to close)
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