This presentation was given in 2012 to the Post Graduate Students Association in the Faculty of Education at the University of Auckland. It covers problems of appropriate data preparation and analysis so as to make claims about phenomena. It covers the following topics:a. the problem of chanceb. sample size determinationc. power analysisd. principles of measuremente. correlation interpretationf. statistical modeling esp. with linear assumptionsg. latent trait theoryh. statistical significance inference, esp. with mean score differencesi. practical significance with effect sizes