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 Description  
 Data:  The facts or numbers that describe something.
Types of Data

There are three different kinds of data:
  • Categorical, such as a person's gender, race, or religion
  • Count, such as the number of televisions in a person's house, number of packs of cigarettes smoked per day, number of visits to the doctor per year.
  • Measurement, such as a person's test score, height, weight.


If data can be represented by one and only one category (e.g., a person's gender) it is called qualitative data.
Categorical Data is qualitative.
Quantitative data are data values that can be measured on a numerical scale.
Counts and measurements are quantitative.
If a data set included the following points, 32, 15, 1, 27, 16, 22, 8, and 12, the range of the data would be 32 - 1 = 31.

Collecting Data

The first step in collecting data is to specify variable names for data you are interested in. The values of the variable are the data that has been collected.

For each case the variable has a certain value. For example, if you had a variable for the person's gender, the variable name might be gender and the values could be M for male and F for female. If the study was interested in the age of a person, there could be a variable named age which had numbers (ages) for the values.


In statistical packages or spreadsheets on the computer, data is usually arranged in tables. Each column contains the values for one variable. The rows contain all the data for a single case.  
Click on the peanut butter jar at the right to see Peanut Butter Data which will be used throughout this page.

How do we get data? There are two ways we can collect data: through observation and through experiments.
Observation
We can record things that we observe in the world around us.
Experiments
We can record measurements as the result of an experiment