Probability Methods for Cost Uncertainty Analysis, 2nd Edition

420 Probability Methods for Cost Uncertainty Analysis

all the physics involved and solved all the differential equations, we could

predict with certainty whether a coin would fall “heads” or “tails.” How-

ever, the combination of inuences acting on the coin is too complicated

to understand in sufcient detail to calculate the physical parameters of

the coin’s motion. So we do the next best thing: we bet that the uncertain-

ties will probably average out in such a way that the coin will fall “heads”

half the time and “tails” the other half. It is much more efcient to con-

sider the deterministic physical process of coin tossing to be a “random” ...