According to the PMI Guide to Business Analysis, one of the best strategies to define appropriate acceptance criteria is to clearly define the performance measures and targets for the solution, such as accuracy, reliability, availability, efficiency, etc. These measures and targets help to evaluate how well the solution meets the stakeholder needs and expectations, and how it contributes to the business value. In this case, since the operations manager is concerned about the accuracy of the new measurement system, a good strategy would be to clearly define the maximum acceptable error rate for the new system, which would indicate how accurate the system should be in order to be accepted by the stakeholder. Quantifying the risks associated with measurement errors, asking for a formal acceptance of requirements documents, or planning a training session for the new system are not effective strategies to define appropriate acceptance criteria, as they do not specify how the performance of the solution will be measured or evaluated. References: PMI Guide to Business Analysis, page 316-317.