You bring up a very good point, Lori: the biggest piece of the "PSK" is training and knowledge (which adds nothing to the pack weight.) If you don't know how to use something in your kit, it's just dead weight.

How much knowledge do you need? It depends on your role on a trip. I'm not wilderness-first-aid qualified. So, although I function often in an assistant-leader role on trips, I make it very clear, up front, to the leader that my role needs to be limited to route-finding, to monitoring the new hikers on the trail (keeping groups in contact as they spread out, hiking sweep, etc.), and to teaching about gear and techniques (how to pitch a tent, or hang a bear bag - that sort of thing.) I also make sure that at least one of the other leaders is properly certified. Usually, at least two are - which means if one of them becomes a victim, we've still got one trained person left. (I used much the same approach at age 10 to determine whether two hand grenades I found in my uncle's WWII footlocker were live or practice.)

When hiking alone, or with perhaps one other companion, I've weighed the lack of formal training into my risk assessment. That's why, in those situations, I never venture off trail, and almost always choose a trip in the "frontcountry," where I'll be passing near roads, or through picnic areas/campgrounds/parking lots every so often, and where I have cell phone coverage most places. Lowering the risk that I'll get hurt or lost allows me to increase the risk of inadequate training, to acheive an overall acceptably low trip risk level. (And yes, to the other two or three accountants on the site, this is modeled after the audit risk approach. )

You can accept higher injury risks if you lower the training risk by getting that additional training. Thanks again, Lori, for reminding us that you need to evaluate the risks of what you're doing, and prepare for them in terms of both equipment and knowledge/skill. Too often, we focus only on gear.