You should only use the capability analysis (Poisson) report when you have an unknown, but high, opportunity count.
For this reason, if you know the opportunity count per unit, and you observe the number of defects, you should use the capability analysis (binomial) report rather than the capability analysis (Poisson) report. The exp(-DPU) approximation always overestimates the true throughput yield, and the severity of the overestimation is dramatic for low opportunity counts. However, note that this approximation is only accurate when the ratio of observed defects to total opportunities approaches 0 (implies either a high opportunity count or a low defect count). This analysis provides a value of defects per unit (DPU), which can be used to obtain an estimate of the throughput yield (a metric commonly associated with Six Sigma) by using the approximation YTP = exp(-DPU). You can optionally run tests for special causes on the U chart. This analysis measures the capability and evaluates the stability of the process, using a U chart. Use this report for processes in which the measurement system is capable of recording the number of observed defects in each unit sampled. The capability analysis (Poisson) report requires that you have a clear definition as to what constitutes a defect and what does not. While the process capability (binomial) report does not integrate the performance of multiple process steps into a single measure, both the capability rollup report and Minitab’s Six Sigma Product Report integrate multiple steps (either attribute or continuous) into a single capability measure (including adjusting for process irregularities). 
To obtain a short-term Z, add the shift (many use 1.5) to the reported Z.
The report also includes a value of Z, which is the long-term Z, rather than the short-term Z typically reported as a metric in Six Sigma projects. This analysis provides the basic capability statistics of "PPM Def", which is the long-term DPMO usually reported as a metric in Six Sigma projects. You can optionally run tests for special causes on the P chart. This analysis measures the capability and evaluates the stability of the process, using a P chart. The process capability (binomial) report requires that you have clear definitions about what constitutes a defect and what does not, and is used for processes in which the measurement system is capable of recording units as defective or not defective.
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