Congrats! From my experience, usually a second interview mean you're 80% in.
Not even close, unless you can say the sum of the other candidates chances are 20%, which is impossible as there is usually another candidate
At best its 50% and thats if only one other candidate made it to 2nd interview, otherwise its usually 33% if 3 made it (=100%/No. of candidates).
Sorry but loose science/maths is one of my largest bug bears
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