Ok, did as you said on your skill point suggestion:

Results:

Player 1: Gained 103% of a skill point(25 y/o)
Player 2: Gained 116% of a skill point(22 y/o)
Player 3: Gained 71% of a skill point(27 y/o)
Player 4: Gained 94% of a skill point(19 y/o)

Can you tell me anything from that data?
P.S. thanks for your help