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Learning Math Home
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Session 1 Part A Part B Part C Part D Homework
 
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Session 1, Part B:
Data Measurement and Variation

In This Part: Asking Questions and Collecting Data | How Long Is a Minute? | Variables

To answer the previous questions, you collected and examined data. Data are defined in terms of variables, or characteristics that may be different from one observation to the next. When we measure these characteristics, we assign a value for each variable. This set of values for a given variable is known as data.

Let's take a closer look at variables. In Problem B4, the variable is the weight of a penny, and the data are the measured weights of the 32 pennies.

Problem B9

Solution  

Look back at Problems B3, B6, B7, and B8. What were the variables in each of these problems?


At least one of these questions has more than one variable. A variable is any characteristic that may change from one observation to the next.   Close Tip

 
 

Some questions, such as "What is your height?," are answered with a number. Answers to questions like "What is your sex?" do not require a number.

We distinguish between variables that are measured in numbers and those that are not. This distinction becomes useful and important when we get to the analysis phase of statistical problem solving. These two types of variables are called quantitative variables and qualitative variables.

Quantitative Variables
Quantitative variables represent numbers or quantities; in fact, they are sometimes referred to as numerical variables. A test score, the number of votes cast in an election, the measured amount of soda in a two-liter bottle -- these are all examples of quantitative variables.

Qualitative Variables
Rather than numbers, qualitative variables represent categories, such as "excellent" or "female," and they are sometimes referred to as categorical variables. The hometown of a college student, the favorite TV show of a politician, and the model of a car seen on a highway -- these are all qualitative variables.

We refer to data in the same terms.

Data are called quantitative if they come from measurements of a quantitative variable.

Data are called qualitative if they come from measurements of a qualitative variable.


Next > Part C: Bias in Measurement

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