Why are people like this? Do we need to bring out the evidence proving that masks saves others' lives? If you wear a mask while not infected, you get a lower chance of getting infected, say 50% effective mask=50% lower chance of getting infected*. As an example, if there was a 1% chance to get infected in a certain interaction, and you wear a 50% effective mask, the virus has 50% odds to get through your 1 mask, and so that drops to 0.5% in that interaction. However, masks work both ways, and so if the infected wears a 50% mask but not you, there is still 1 mask, leaving a 0.5% chance to get infected, assuming the same rate of infection as above (i.e. 1% with 0 masks). If both wear a mask, the virus has 50% odds to get through 1 mask, and therefore a 25%** chance to get through both, which turns the 0.5% chance of infection to 0.25%. Both situations improved the odds of the person not getting infected.

The expected value (EV for short) in terms of the average number of lives lost while wearing a mask (vs. not wearing one) would be as follows.

EV of wearing a mask= # of people interacted with*chance for an infection to occur while wearing a mask*chance that you can infect*death rate

EV of not wearing a mask= # of people interacted with*chance for an infection to occur while not wearing a mask*chance that you can infect*death rate

The difference in EVs= # of people interacted with*difference between chances for an infection to occur while wearing and not wearing a mask*chance that you can infect*death rate

The difference is the only necessary part and should be negative (negative here means less, which translates it to wearing a mask having fewer lives lost compared to not wearing a mask, which means wearing a mask saves lives, which the poster of this meme does not believe in and thus needs to be proved). # of people interacted with should be positive. (Can't live without ever going out and buying essential supplies, can you?) The difference in infection rates should be negative as said earlier. The chance you can infect others is positive since you could be in a stage where symptoms are not apparent yet but can infect. Death chance is obviously positive, people are dying. positive*negative*positive*positive =negative =saved lives

*not how effectiveness really works, but rather a simplification.

**not exactly correct since technically some of the particles just always slide through for example, but the point is it helps.