effectiveness

There are several answers to this question. One was overheard the other day among a bunch of well educated people oriented towards science who were taking a break from their job. Person 1: "So, how effective is the seasonal flu shot?" Person 2: "I heard about 1%. If you get the flu shot, you'll have a 1% difference in if you get the flu." Person 3: "That's crazy. I don't know where you are getting your data from. It can't be 1%, but I admit I don't know what the actual answer is, but it can't be that." Persons 4 through 6: "Well, if YOU don't know, and HE says 1%, I'm going with the 1%.…