You and a friend have decided to play a game to drill your statistical intuitions. The game works like this:
You have a bunch of red and blue marbles. To start the game you grab a handful of marbles of each color and put them into the bag, keeping track of how many of each color go in. You take turns reaching into the bag, guessing a color, and then pulling one marble out. You get a point if you guessed correctly. The trick is you only have three seconds to make your guess, so you have to think quickly.
You've decided to write a function, guessBlue() to help automatically calculate whether you should guess "blue" or "red". The function should take four arguments:
- the number of blue marbles you put in the bag to start
- the number of red marbles you put in the bag to start
- the number of blue marbles pulled out so far, and
- the number of red marbles pulled out so far.
guessBlue() should return the probability of drawing a blue marble, expressed as a float. For example, guessBlue(5, 5, 2, 3) should return 0.6.