what is the difference between epistemic and aleatory uncertainty. Give and example for each. Give an example when one can turn into another.
Aleatory uncertainty (or statistical uncertainty) is the physical variability or natural randomness present in the system or environment. Cannot be reduced.
An example is an arrow fired the exact same way every time will not hit the same spot every time.
Epistemic is due to lack of knowledge, data, or deficient models. This can be reduced by creating better models and getting more data.
An example is limited data (such as earthquakes or structural failures).
An example is when concrete is poured into a foundation, it turns from epistemic (at design) to aleatory, once it hardens.