what is the rule of the thumb(apply in analysing data)?

Answer 1

I rule and when I put my thumb up, the person lives...
Seriously, what the hell are you talking about? What type of analysis and what type of data? Tell us where you heard the expression used. In English, a "rule of thumb" is a colloquial term meaning any sort of general guide which usually works when trying to figure something out - it totally depends on the context in which it was used as to what it means.

Answer 2

First best approximation (ie look at thumb as if trying to estimate size of distant building).

In analyzing data - take first approximation and try and solve for variables and see if guess fits