EVALUATION OF 2 ASSUMPTIONS - SINGLE STRAIGHT-LINE, AND SINGLE NORMAL-DISTRIBUTION

Using graphical and statistical approaches, Laszlo Endrenyi and Mayank Patel describe methods that answer two frequently asked questions: 'Can the data be characterized by a single straight line, or should a more complex model be invoked?' and 'Do the observations follow a single normal distribution, or is there evidence for deviations from this assumption, including the possibility of bimodality?' These methods complement those addressed in a recent Principles article by Dick Barlow.