
168 ◾ Software Metrics
with a chemical, “not used” in soware engineering may be dicult or
impossible to control. If we tell designers not to use a particular method,
they are likely to use an alternative method, rather than no method at all.
e alternative method may be hidden, based on how they were trained
or what experience they have, rather than an explicitly dened and
er of factors
Use >1 factor: look at
treatment combinations
Use blocks and levels
to ensure unbiased
assignment
Investigating
effects of a
variable?
Y
Y
Y
N
N
N
N
Y
Y
N
No experiment needed
Use one factor: set of
competing treatments
Use factors to distinguish
cases or
circumstance ...