How to measure visitor engagement

Part 1: session-based indices

Click-Depth Index (Ci)

is the percent of sessions having more than “n” page views divided by all sessions.
Recency Index (Ri)

is the percent of sessions having more than “n” page views that occurred in the past “n” weeks divided by all sessions. The Recency Index captures recent sessions that were also deep enough to be measured in the Click-Depth Index.
Duration Index (Di)

is the percent of sessions longer than “n” minutes divided by all sessions.
Brand Index (Bi)

is the percent of sessions that either begin directly (i.e., have no referring URL) or are initiated by an external search for a “branded” term divided by all sessions (see additional explanation below)
Feedback Index (Fi)

is the percent of sessions where the visitor gave direct feedback via a Voice of Customer technology like ForeSee Results or OpinionLab divided by all sessions (see additional explanation below)
Interaction Index (Ii)

is the percent of sessions where the visitor completed one of any specific, tracked events divided by all sessions (see additional explanation below)

Part 2: binary weighting factors based on visitor behavior

Loyalty Index (Li)

is scored as “1″ if the visitor has come to the site more than “n” times during the time-frame under examination (and otherwise scored “0″)
Subscription Index (Si)

is scored as “1″ if the visitor is a known content subscriber (i.e., subscribed to my blog) during the time-frame under examination (and otherwise scored “0″)

You take the value of each of the component indices, sum them, and then divide by “8″ (the total number of indices) to get a very clean value between “0″ and “1″ that is easily converted to a percentage.

Given sufficient robust technology, you can then segment against the calculated value, build super-useful KPIs like “percent highly-engaged visitors” and add the engagement metric to the reports you’re already running.

Engagement: is an estimate of the degree and depth of visitor interaction on the site against a clearly defined set of goals.

"engagement = attention * emotion"

website:http://blog.webanalyticsdemystified.com/weblog/2007/10/how-to-measure-visitor-engagement-redux.html