You can teach a skill, but you can't learn it for someone. E.g., you can teach a skill to an administrative assistant the same way you teach it to a cop, but you can't learn it for them and you can't do it for them. You can, however, develop traits im folks who are receptive by teaching them behaviors.
I'm talking about the office worker, computer programmer, teacher, hair stylist or otherwise non-violent person who has never been a bouncer, soldier, cop, bodyguard or hitman. Let's call this group "almost everyone." These folks who take "self defense" classes aren't learning skills that will make them more safe. Or to be fair, there is zero evidence that they are. They MIGHT be learning behaviors that will help them be more safe, but I don't think these behaviors are specific to self defense training. Skills development in a self defense class is going to be limited, regardless of how long they train.
To be more specific, for these regular people, I think the aspects of a "self defense" course that actually help are not specific to self defense training. In other words, among the traits they are developing are self-esteem, confidence, a sense of community, positive role models, a fighting spirit, fitness, and athleticism (well, those last two are not always intrinsic to self defense classes). You can develop these same traits doing Zhumba or Tae Bo, or training for a Tough Mudder course.
Look at it like this,
@Buka. Look at all the tenuous leaps of faith one must take for which there is no supporting evidence, and in some cases, evidence to the contrary:
1: You have to believe that the skills you are learning actually work for someone.
2: ... that the techniques will actually help you and not make things worse.
3: ... that you can perform a technique at all.
4: ... under pressure, in the safety of training.
5: ... outside of training, in some context (i.e., on the job, in a ring)
6: ... AND then in the context of self defense.
There are some folks teaching self defense to other folks here who think they're at 6, but are really stuck at somewhere between 3 and 4. The good news is, if you reach step 5, it's a relatively short leap to step 6.
Going back to the point I led off with, we commonly see people teach a system and then build expertise in a system. Can this work? Hard to say. And is there anything wrong with it? Nothing at all. If you have a system you teach, call it Buka-do, and you teach people to nutshot and curbstomp bad guys, it's up to you to establish the criteria for evaluating their performance. You could absolutely teach someone to be an expert in Buka-do. Will that make them able to fight off a bad guy? Absolutely no way to know.
Now, I understand that some guys like Gerry insist that you can skip step 5, but Gerry has yet to offer an example of someone developing skill in something without ever actually doing it... other than self defense, of course.