You don’t have to be a statistician to play bridge. You don’t have to know binomial distributions or how to calculate exact odds for the distribution of the missing cards in a suit. It really is helpful, though, to know the approximate odds for how the missing cards in a suit will split when you are the declarer. I’ll try not to give you raw percentages, but I’ll provide you some mnemonics to help you remember them.
There’s a great page on these odds at http://www.rpbridge.net/4b00.htm
Suit Break Thumb Rule: If you are missing an odd number of cards they are more likely to break nearly evenly more often than not. If you are missing an even number of cards they will split evenly less often than they will split unevenly. For example, missing 5 cards they will split 3-2 or 2-3 more often than not. If you are missing 6 cards they will split 4-2 or 2-4 more often than they will split 3-3.
Missing 2 Cards: The 1-1 split is only slightly more likely than the 2-0 split. Usually you should play to drop a missing King.
Missing 3 Cards: The 2-1 split is a little bit better than a 3 out of 4 chance.
Missing 4 Cards: You will get a 2-2 split approximately 4 times out of 10. (Mnemonic: 2+2 = 4). You should play to drop a missing Queen in the absence of other information.
Missing 5 Cards: They will split 2-3 approximately 2 out of every 3 times. You should play to finesse a missing Queen in the absence of other information.
Missing 6 Cards: They will split 3-3 a little more than 1 out of every 3 times. They will split 2-4 nearly one-half of the time. (Mnemonic: 2/4 = 1/2).