Page 63 - Statistics for Dummies

Ordinal data mixes numerical and categorical data. The data fall into catego-
ries, but the numbers placed on the categories have meaning. For example,
rating a restaurant on a scale from 0 to 4 stars gives ordinal data. Ordinal data
are often treated as categorical, where the groups are ordered when graphs
and charts are made. I don’t address them separately in this book.
Data set
A data set is the collection of all the data taken from your sample. For exam-
ple, if you measured the weights of five packages, and those weights were
12, 15, 22, 68, and 3 pounds, those five numbers (12, 15, 22, 68, 3) constitute
your data set. If you only record the general size of the package (for example,
small, medium, or large), your data set may look like this: medium, medium,
medium, large, small.
Variable Chapter 4: Tools of the Trade 47
A variable is any characteristic or numerical value that varies from individual
to individual. A variable can represent a count (for example, the number of
pets you own); or a measurement (the time it takes you to wake up in the
morning). Or the variable can be categorical, where each individual is placed
into a group (or category) based on certain criteria (for example, political
affiliation, race, or marital status). Actual pieces of information recorded on
individuals regarding a variable are the data.
Population
For virtually any question you may want to investigate about the world, you
have to center your attention on a particular group of individuals (for example,
a group of people, cities, animals, rock specimens, exam scores, and so on).
For example:
✓ What do Americans think about the president’s foreign policy?
✓ What percentage of planted crops in Wisconsin did deer destroy last year?
✓ What’s the prognosis for breast cancer patients taking a new experimen-
tal drug?
✓ What percentage of all cereal boxes get filled according to specification?

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