Q: Given a scientific passage and an answer, generate a question for the given answer.
Passage: Chemical reactions in the real world don't always go exactly as planned on paper. In the course of an experiment, many things will contribute to the formation of less product than would be predicted. Besides spills and other experimental errors, there are usually losses due to an incomplete reaction, undesirable side reactions, etc. Chemists need a measurement that indicates how successful a reaction has been. This measurement is called the percent yield. Answer: percent yield
A:
What is the term for proportion of amount of product actually produced in a chemical reaction versus predicted amount ?