Assume 26 letters, space, CR, comma, exclaim, question, and apostrophe is used for itself and double-quotes; no extra keys. Oh, So each stroke has a 1/32 chance of being correct for a given desired word/sentence. Multiply that by itself for each character. A five letter word is 1/32^5, which means out of ~33MM tries, you should see that particular word once. “This is a test sentence.” requires 1,329,228,000,000,000,000,000,000,000,000,000,000 attempts to statistically occur a single time.
And like I said, all of this assumes the monkeys only have the keys they need. Most keyboards have 75 to 100 keys, not just 32. And, some keys need a hold-shift and press other key (?,”,!), and I have no idea how to add the immense extra unlikelyhood of key combos. You’re probably now looking at overall chances of one in a googelplex, or even less.