Applying Pareto Analysis for all kind of issues even for those issues where the complete set of data isn't available (E.g. For the scenario documented here).
Not knowing the fundamental idea or principles of Pareto Analysis and usage of cause and effect (80/20) in reversed order (20/80) to substantiate the hypothesis.
Wrong classification of data leads to wrongful identification of the cause. Collection and classification of data are the foundation of Pareto Analysis.
Thank you. Your feedback is welcome.