Not too good with maths, /sci/, can someone tell me what the effective percentage increase is based on stat and dice rolling?

Lets say both people are rolling a 1d10. One person has adds a +10 to their roll, the other person adds a +11 to their roll. Percentage wise, how much more effective is the person with the +11 at rolling higher than the person with the +10?

Is he simply 10% more effective at rolling higher on average?