Some Observations on the D Development Process

[Adam D. Ruppe]

On Friday, 5 January 2018 at 06:20:54 UTC, Patrick Schluter wrote:
> The only people I ever saw with a flu (I mean a real influenza) 
> had all one thing in common: they all had gotten the flu shot.

That's a case of selection bias: the people who get the shot tend 
to be those who are already at high risk of getting the flu.

The shots cover common strains - or at least what they think will 
be common strains - but they don't cover all of them. So consider 
the math: let's say you judge yourself to have a 20% chance of 
getting the flu, so you get the shot. It cuts your odds by about 
50%... but that still leaves you with a 10% chance of getting one 
of the other strains.

The general population, on average, has about a 5% chance of 
catching the flu... so even with the shot, you, in the very 
high-risk pool to begin with, are still more likely to get it 
than the average person, but that doesn't mean the shot was 
ineffective, and, of course, it certainly doesn't mean the shot 
CAUSED it.