Power
Power turns up in 2 fields: railroad, statistics. Here is what it means to the people in each one.
Power in railroad
The locomotives assigned to a train, or locomotives in general.
Railroaders rarely say locomotives when they can say power: a train has power on the head end, the yard is waiting on power, and a terminal is power short when there are not enough units for scheduled departures. Lite power is a set of locomotives running without cars. Planners measure power in horsepower per trailing ton, and a train with too little of it stalls on grades or crawls across a division.
"Our power's coming in on the Q train, so we're on hold until they cut it off and fuel it."
Power in statistics
Probability that a test will detect a real effect of a given size, set by sample size, noise and alpha.
Power is 1 minus beta, where beta is the Type II error rate, the chance of missing an effect that is really there. It rises with sample size, effect size and alpha, and falls as noise grows. Studies are usually sized for 80 or 90 percent power to detect the smallest difference that matters; detecting a 1 sigma difference between two means at alpha 0.05 with 90 percent power takes about 22 units per group.
"Four wafers per leg gives you maybe 30 percent power for a 1 nm shift. Either add wafers or don't bother running it."