1. Continuous improvement in predictive maintenance
RULE = Remaining useful life estimate
It is commonly called the "Remaining Useful Life Estimate" or by the acronmym "RULE".
One performance measure of a predictive maintenance program is the spread of the distribution around the mean (i.e. around the RULE). This spread  is quantified by the standard deviation.
Conditional MTBF
Continuous improvement in the RULE occurs over time as more experience is gathered. Not only is the RULE adjusted, but the spread narrows.
Is the well-known MTBF, except that it is measured from the current moment. That is, the moment when one needs to make an on-condition maintenance decision.
And narrows further.
Improving
RULE
The RULE improves
Increasing
confidence
Confidence in prediction increases in a measurable way so that it may be reported as a CBM KPI.
Conditional
Density
Function
Continuous improvement in predictive maintenance t0
Working age
Current time

2. Conditional Density in EXAKT