This paper proposes a new typology for understanding common research errors that expands on the four types of error commonly discussed in the research literature. Examples are presented to illustrate Type I and Type II errors, errors related to the interpretation of statistically significant and nonsignificant results respectively, with attention given to the control of both types of error. Then an explanation of typical errors that fall into the Type III (incorrect inferences about result directionality) and Type IV ("effects error") categories is offered, along with examples of erroneous conclusions researchers draw when committing these errors. Six additional types of errors are proposed for addition to the typology, with a discussion of how attention to these newly identified error categories can be useful in improving the quality of educational research. These error types are: (1) internal replication error; (2) reliability generalization error; (3) heterogeneity of variance/heterogeneity of regression error; (4) test statistic distribution error; (5) sampling bias error; and (6) degrees of freedom error. (Contains 66 references.) (SLD)