Originally Posted by
350htrr
OK I think I understand now... Less than 1% chance of being in an accident, less than 1% chance the helmet helps/needed if in an accident. So Less than 0.01% chance the helmet is useful for the average cyclist.? But once in an accident where head hits the pavement the helmet can/could be beneficial 65% of the time...
That is my reasoning through the numbers. But it was 5% chance of injury accident (adjusting for extra helmeted accidents not reported), and 19% chance that a helmet would be needed, which by chance .05 x.19=.0095, close enough to 1% for that final number (not .01%) Then that times .65 just as you reasoned.
edit: I'd like to point out that this makes sense if you're looking at
total injuries for everyone, for example you want to make something mandatory, or you're trying to decide if it's worth the effort of advocacy. This particular calculation is rather less useful for an individual.