Survivorship Bias

(Sarcasm is OFF for this post, except for a tiny bit at the end.)

One good thing about the fake “pandemic” is that I’m learning about the various ways one can lie with statistics. Brian Mowrey, the author of the excellent Unglossed, mentioned something called “survivorship bias” in his article about stillbirths in Singapore:

Literally any “intervention” can appear to make pregnancy “less risky” simply by being applied mid-way through the window. If you resolve to give cupcakes to soldiers in the middle of a battle, your cupcake-receiving soldiers will survive more than the soldiers who started off at the beginning of the battle, because they have already lived to the point of your arriving to give them a cupcake. Sadly, this does not mean your cupcakes are protective, and you should not market them as such.

Here’s a simple “cupcake” example:

Suppose you are a general sending 200 soldiers into battle, and you know that 10% of them will die each week (probably better odds than trench warfare in WWI). After the first week, 20 of the soldiers have died. Then you give half of the remaining 180 (i.e., 90) soldiers a cupcake. A week later, another 10%, or 18, have died. Of these 18, 9 had received a cupcake and 9 of them had been cupcake-deprived. So in those two weeks, 29 of the soldiers who had died had not received a cupcake, while the remaining 9 who died had received a cupcake.

This proves that cupcakes are a safe and effective way to prevent death in battle. In fact, we can calculate the efficacy of cupcakes.

The percentage of un-cupcaked soldiers who died is 29/200, or 14.5%.

The percentage of cupcaked soldiers who died is 9/200, or 4.5%.

The reduction in death rates effected by cupcakes is 14.5%-4.5%, or 10%.

The efficacy of cupcakes is the cupcake-induced reduction in death rates, divided by the death rate of the un-cupcaked group, 10%/14.5%, or 69%.

This means that in our example, cupcakes are 69% effective against death in battle! Not only that, but they are totally safe! This should cause the stock price of cupcake makers to go through the roof, and the DoD should mandate cupcakes for all soldiers.