Now that’s nice and all, but for practical purposes I think an inverse concept is perhaps even more useful. By inverse I mean rejection levels. Or, as I like to call them, what-the-hell-I’m-absolutely-not-willing-to-accept-that levels. The idea is simple enough: rejection levels signify the worst attribute levels you’re willing to accept. A value worse than that means you’ll discard it immediately and look elsewhere.
The benefit is that if you have many alternatives, rejection levels can be used to make the search space smaller very fast. Imagine you’re buying a bike, and there are two criteria: cost and quality. You probably have some aspiration levels – the ideal bike. That’s reflected in the upper left corner (low price, terrific quality). But that only tells us the portion of the search space with the best alternative, but unfortunately very likely a non-existing one. Looking at the picture below, it’s clear there’s still a lot of search space remaining.
To avoid this, rejection levels are a great technique. If the price goes above the rejection level, you can confidently say thanks, but no thanks and just move on. By making the rejection decisions with a rule that you’ve committed to beforehand is much, much easier than mulling over each and every option you come across.