
48 Empirical Research in Software Engineering
b. For continuous variables (variables that do not have any specied range), the
following commonly used effects are of interest:
i. Mean difference: This measure is used when a study reports the same type
of outcome and measures them on the same scale. It is also known as “dif-
ference of means.” It represents the difference between the mean value of
each group (Kictenham 2007). Let
and
be the mean of two groups
(say g1and g2), which is dened as:
Mean differenceX X
g1 g2
ii. Standardized mean difference: It is used when a study reports the same
type of outcome measure but measur ...