A bag contains 5 red marbles, 6 blue marbles and 4 green marbles. Susie selects a marble and returns it to the bag before selecting another marble. If susie selects a red marble 6 out of 20 times, what is the experimental probability that the next marble she selects will be a red marble?

Whilst it seems an unlikely scenario, unless we have reason to believe Susie is not making a random choice but is making a free selection, then the previous withdrawals make no difference as the marble is returned each time. Therefore the probability is the same as at the beginning which is 5 red / 15 total marbles, or 1 in 3.