 In a study of the use of econometrics in major economics journals, McCloskey concluded that some economists report p-values (following the Fisherian tradition of tests of significance of point null-hypotheses) and neglect concerns of type II errors; some economists fail to report estimates of the size of effects (apart from statistical significance) and to discuss their economic importance.She also argues that some economists also fail to use economic reasoning for model selection, especially for deciding which variables to include in a regression.In some cases, economic variables cannot be experimentally manipulated as treatments randomly assigned to subjects.