I use random() in a code to calcuate the times to win, but the result is as expected

def simNGame(probA, probB, n):
# simulate n games 
# prob is the chance to win of person A or person B, n is the times of games
# return the number of wins of A and B
winsA = 0
winsB = 0
for i in range(n):
    scoreA, scoreB = simOneGame(probA, probB)
    if scoreA > scoreB:
        winsA += 1
    else:
        winsB += 1
return winsA, winsB

def simOneGame(probA, probB):
    # simulate 1 game
    # return the score of A and B
    scoreA = 0
    scoreB = 0
    serving = 'A'
    while not gameOver(scoreA, scoreB):
        if serving == 'A':
            if probA > random():
                scoreA += 1
            else:
                serving = 'B'
        else:
            if probB > random():
                scoreB += 1
            else:
                serving = 'A'
    return scoreA, scoreB

def gameOver(scoreA, scoreB):
    # check the game is over or not
    return scoreA == 15 or scoreB == 15

This code is used to simulated the racquetaball. when I ran it with two people with same changce to win, I noticed that winsB was always 4700+ and winsA was always 5200+, so I try this:

while True:
    a, b = simNGame(0.5, 0.5, 10000)
    print a > b

All of the results is True, but I cannot check any errors in my code.why,thanks