thesis - Faculty of Information and Communication Technologies ...

Chapter 5. Growth Dynamics
Median
0 1 2 3 4 5 6
0 10 20 30 40
Release Sequence Number
Number of Methods
Out-Degree Count
Public Method Count
Figure 5.2: Change in Median value for 3 metrics in PMD.
224, 226, 251, 274, 295, 296] summarise data using simple descriptive
statistical measures.
Comparison of different distributions may provide some insight, but require
skill to interpret, particularly given the range of measures that can
be used and the different population sizes that might be encountered.
5.1.2 Distribution Fitting to Understand Metric Data
A more recent method to understand software metric data distribution
involves fitting the data to a known probability distribution [21,55,
118, 223, 270, 299]. For example, statistical techniques can be used to
determine if the Number of Methods in a system fits a log-normal distribution
[55]. The motivation for fitting metrics to known distributions is
driven by the notion that it can help explain the underlying processes
that might be causing specific distributions [209,287]. Furthermore, if
the fit is robust and consistent we can infer information from the distri-
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