In: Statistics and Probability
About 1 in a million airliner flights crash. You're flying on an airliner and the right engine suddenly catches fire. While everyone else is panicking, you turn on your cell phone (never mind airplane mode-- this is an emergency!) and do a quick check of the statistics.
You discover that, 1 in 100 crashes involve an engine catching fire, but an engine only catches fire in 1 in 100,000 flights that don't crash. So the probability that an engine would catch fire if you were going to crash is 1/100, but the probability that an engine would catch fire if you were not going to crash is only 1/100,000!
What is the strength factor of the evidence that the engine caught fire, in favor of the claim that you're going to crash?
a. 10
b. 1000
c. 1/100
d. 100
strength factor of the evidence that event A occurs, in favor of the claim that event B occurs
= P(event A | event B) / P(event A | event B not occuring)
strength factor of the evidence that the engine caught fire, in favor of the claim that you're going to crash
= ( probability that an engine would catch fire if you were going to crash) / ( probability that an engine would catch fire if you were not going to crash )
= (1/100)/(1/100000)
= 1000
Answer option b : 1000