One of the most important disadvantages when discussing case studies is the possible errors in data collection and interpretation. In Dr. Crawford's book, Introduction to Research: Less Fear, More Intuition, Crawford explains the biased data collection that disqualifies the findings of several case studies. Disqualifiers such as biased selection and biased testing produce a big problem for researchers because if data is collected biasedly, the entire case study could be considered flawed. Therefore it is important for the researcher to carry out the experiment with a single-blind or double-blind study to reduce potential threats associated with data collection and interpretation.