Justifying Answer by Matt Cutts to the Webmaster Question “How does Google think about search quality when it relies on subjective signals?”

If you are looking for answer to your confusing question that How can Google be confident with their SERPs, when it is depending on intrinsically subjective signals which have an impact on the websites display that is making use of human “Quality Raters” for evaluating the entire list of domains without giving the context of the search query itself. In this Google Webmaster Help Video Matt Cutts answers this question by saying that Algorithms are intrinsically subjective for the reason that they are designed and developed by individuals who have a specific viewpoint, strategy or bias for ranking the websites which is just fine.
He as well states that this is as well the reason why he looks for how Google will be thinking or approaching such problems. That is where the webmasters can now gain some information beyond the now & can prepare themselves for the future. Watch out this video by Matt Cutts for more detailed answer to this question :