What's the difference between Fixed Dose Procedure and LC50??

Question

these two are known as useful tools in toxicity testing...but how do they differ??

Answer 1

"FDP uses about 10 to 20 animals to find the dose producing toxicity signs but not death, and from there predicts the lethal dose.

LD50 (lethal dose 50%) uses about 60 to 80 animals to find a dose killing 50% of animals within a given time."

So basically one is an extrapolation while the other is an actual statistical value.