Over at SEO Black Hat, QuadsZilla demonstrates correlation between traffic, specifically Google traffic, and bounce rate, claiming that bounce rate is being used to determine quality and factoring into rankings. Except his or her graphs show direct, rather than inverse, relationships between traffic and bounce rate. In other words, in those graphs, on days when Google traffic (and traffic overall) was down, the bounce rate was down, too.
This runs counter to what one might expect if bounce rate were being used to determine quality from a SERP perspective. A poorly designed or ill-thought-out landing page might cause irrelevant traffic to bounce, meaning bounce rates would increase, and if that was being used to determine relevance and quality, surely traffic would begin to decrease (and gradually, rather than appearing all at once on the same days as the graphs indicate) over time in relative opposition to the bounce rate.
Instead I’d posit a different interpretation: that the marketing mix changed on those days. Something went afoul (from the SEO’s perspective) with rankings in Google, and traffic coming from Google decreased. At the same time, bounce rate decreased. That suggests that less irrelevant traffic was coming to the site. The traffic that remained was likely comprised heavily of direct type-in and referral traffic, which would be expected to perform better from an engagement perspective. I would venture to guess that conversion rates increased in relative inverse proportion to the fall in bounce rates, too.
To take it a step further from analysis into philosophy, this is what makes SEO such art and science. Many SEOs get caught up in the technique and fancy footwork of achieving higher placements in the SERPs with little regard for whether they’re going after the right traffic. Traffic without some form of engagement is meaningless. There’s no reason to drive scores of visitors to your site (are you listening, Digg-baiters?) if the audiences you’re driving will never care about your content or your offering.
SEO for SEO’s sake is silly. SEO for the sake of findability and end user targeting is a beautiful thing. If you don’t know the difference, you’re adding noise to an already noisy space.