>Your detailed message explains or resumes a lot of points I mentioned. But, as additional information, the 90 seconds is not in effect. It is like one person would use one account, do several clicks to read messages, post a new thread or a reply and switch into the other browser to use the other account and do the same. During that time, no other activity is done on the other account but an auto refresh, if the session remained opened. Yes, someone can log off the site from the main page. But, I have no record of that during that yoyo game that was played.
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>But, without any doubt, someone tried to fool the system, Grover Lipscomb does not exist, contains a lot of bogus information in this account and the related activity was combined with the other account as a flip flop. But, as I said in the other thread, it was discovered because the member didn't think of that. For example, if one person would like to fool the system like that, that person could have done some mix hits on a regular basis which would have made pratically impossible for me to find the source. But, it was so precised, and it happened at various interval with exactly the same pattern that it made no doubt that it was the same person.

OK, so you're saying explicit or implicit logoffs didn't always occur. It looks like you're looking for evidence of "simultaneous" activity, the idea being if such is found, they must be different people. Simultaneous activity could be things like:

- hits from the 2 different IPs/accounts within a very short time period (e.g. a few seconds)
- interleaved hits over some reasonable time period i.e. not just from one account or the other

But, if I'm correctly interpreting what you've been saying so far, you have seen neither of the above for Kevin and "Grover", so you believe it is one person, first paying attention to one account, then to the other.

IMO that's a reasonable interpretation. However, I agree with Tracey - I think it would be a good idea to run your analysis for "Grover" vs. other active members, and also for Kevin vs. other active members. If any of those analyses raise the same flags, then the behaviour may not be unique, or your analysis algorithm may be flawed (or both).