
158 ◾ Software Metrics
Many investigations involve more than one independent variable. In
addition, the experiment invokes changes in the dependent variable as one
or more of the independent variables changes. An independent variable is
called a factor in the experimental design.
EXAMPLE 4.14
A study to determine the effect of experience and language on the productiv-
ity of programmers has two factors: experience and language. The depen-
dent variable is productivity.
Various values or classications for each factor are called the levels of
the factor. Levels can be continuous or discrete, quantitative or qualita-
tive. In Example 4.14, we ma ...