The reliability and validity of the
selected research method are subjects to which every researcher is bound to address
himself when representing the findings and conclusions of his/her work. In this
study we will discuss the reliability, validity and philosophical aspects of
the Delphi method, first with a small literature review and then by
representing two different surveys conducted using the Delphi method. The point
of view in our report is the usability of Delphi in collecting qualitative data
for software engineering research. The most significant features of the Delphi
method are its recursion and the possibility to get immediate feedback and
evaluate one’s own answer. Although there are many forms of Delphi techniques, these
features exist in one form or the other in all Delphi variations. In
Delphi-based surveys, the minimum number of participants is smaller and
participants are not selected at random but because of their particular
expertise. Among the traditional research methods this is seen to cause the
risk of bias and endangering both reliability and validity. In the Delphi method,
the recursion produced by three or more rounds, the expertise and – in most
cases – anonymity of participants, and the opportunity to evaluate and argue
one’s own answer after having seen the other opinions and arguments are thought
to guarantee the quality of well-planned and well-conducted research.