This might be more suited to r/NoStupidQuestions but it's so common in historical discussion that I thought I'd ask here in order to get a definitive answer. I just hope I can word it in a way that makes sense. Anyway my question is this:

Is infant mortality really factored into the "life expectancy" of past eras and ages?

And if so, how does that not completely skew the data or make it almost irrelevant for "regular" people to understand? I mean, when people hear something like "The average life expectancy in medieval Europe was 35" most people assume that people back then usually died before their 35th birthday. And then someone will come along and say "Oh no. That number is low because of infant mortality rates".

"Well gee, that's great! Thanks for nothing then".

Seriously though, it just seems sort of pointless to factor in infant mortality rates when talking about life expectancy because to the layman, once you do this, it gets extremely confusing. Almost to the point that it seems like someone's trying to trick us. But like I said I'm not 100% certain this is actually the case because the only people I've ever heard say that infant mortality is factored into life expectancy rates are people who are not actual historians.

I'd really like to get to the bottom of this because as someone with an interest in history the idea of "Life Expectancy" has always been a confusing mess for me.