[This paper builds upon the work of Burgstahler and Jiambalvo (1986a, 1986b) on auditors' estimation of error through sampling. Burgstahler and Jiambalvo used a ball-and-urn inference model to argue that the isolation of sample errors violates professional auditing standards. They speculated that context-specific data about sample errors induces uniqueness perceptions that, in turn, cause auditors non-normatively to isolate the errors. We extend their research by manipulating two variables they suggested, but did not test: (1) containment information, which indicates whether the discovered error is limited to a well-defined subpopulation of unsampled items; and (2) perceived frequency of errors, which is directly related to the similarity of an error to other potential errors. Our results show that containment information strongly affects the projection-isolation decision, regardless of the perceived frequency of the error. In our empirical work, error frequency also affects the judgment. These findings suggest that containment information does not affect the decision solely by inducing perceptions of uniqueness but rather has a direct effect on it. Additional research is needed to describe and understand more fully this important judgment.]