When you run the simulation for this model, the Cycle Time forecast chart opens (Figure 166, The Cycle Time Forecast with Process Capability Metrics, following). Because the forecast is defined with an upper specification limit and a target, the chart is displayed in Split View with the forecast chart beside the process capability metrics. The message with the metrics indicates that the distribution is non-normal (the normality test failed), so capability metrics are calculated from the forecast values.
Notice that marker lines are displayed for the USL and target. Because the USL is defined, the maximum certainty grabber is automatically set to that value. Because no LSL is defined, the minimum certainty grabber is automatically set to –Infinity. The Certainty field contains 72.31; about 72% of forecasted values fall below the USL.
Looking at the process capability metrics, the forecast distribution is not normal, so the Z scores are not generally appropriate to use. The p(N/C)-above (defects above the USL) is about .28, which confirms the certainty level shown in the forecast chart; more than one-quarter of the forecasted values fall above the USL. The Cpk-upper and Cpk are about 0.21, where you had hoped to see at least 1.00 (the 3-sigma level). The loan specialists you interviewed were correct — cycle time variation is large.
You generate a sensitivity chart (Figure 167, Sensitivity Chart for the Cycle Time Forecast) to determine which of the loan processing steps has the most influence on the Cycle Time forecast variance. To do this, select the forecast chart and choose Forecast, then Open Sensitivity Chart.
Figure 167, Sensitivity Chart for the Cycle Time Forecast shows that the loan processing step with the greatest effect on cycle time variance is Document Verification (Step 3). Obviously, this is an ideal target for improvement.
