Which index in Analytic is important for SEO?

Well, as I say, you need to be careful how you interpret bounce rate, and obviously its significance will vary, depending on your site.

Perhaps you have a site advertising a bricks and mortar business. I want to know your opening hours so I can visit. I check your site, immediately find the information I want, and leave again, thinking “What a great site! It’s so easy to use.” So what looks like a “bounce” is a happy visitor.

On the other hand, your business might be entirely on-line, so that scenario is not applicable. I visit your site and spend quite a long time visiting various pages. You interpret that as me liking your site, because I’ve hung around for a while, but I might just as easily have left thinking “Well, that was a waste of time. I couldn’t find what I wanted at all. Rotten site - really badly laid out. I’m not going back there.”

My point being, that bald statistics don’t tell the whole story.