Chapter 6. Data and Data Types
In This Chapter
Understanding the special properties of dates and times
Working with data that comes at regular intervals
Creating multiple response sets
Copying variable definitions from another file
A data type is nothing more than the definition of what a number means. Without a definition, a number serves no purpose. For example, the number 3 could have entirely different meanings. It could be a number of miles, or an answer to a multiple-choice question, or the number of jelly beans in your left pocket. The data type is more than just a tag — it determines how the value can be manipulated. For example, 3 miles can also be written as 15,840 feet or as 24 furlongs. Some data types require special arithmetic. Telling time is an example: If the number 50 represents the number of minutes past 2 o'clock, adding 15 to it will result in the number 5 — that is, the number of minutes past 3 o'clock.
Dates, times, and schedules are important in statistics, but they're usually hard to work with arithmetically. Fortunately, all you have to do is tell SPSS how you'd like to handle them, and all the hard calculating can be taken care of for you. Arithmetic that normally would be tedious and boring can be automated by assigning the appropriate data types. And if you've worked on a table and arrived at some nifty variable definitions, you can copy them into a new table (or even into an old table). This chapter discusses the nuts and bolts of creating such magic by working ...