As an earlier poster commented, if the Enterprise had a 90% chance of surviving each of the 79 episodes, their overall chance of surviving all those missions would be roughly 4000 to 1 against. Not good odds. 99% per adventure would put them at almost 2 to 1 against. Not great, but much better!
I used to think Spock calculated all those odds to a tenth after the decimal because the show was written by English majors who didn't know about significant digits. But if you take into account the unknowns and intangibles, with the crazy precision Spock was announcing, it's clear he was joking with Kirk. Something only buddies would do. Which is another kind of Vulcan whopper.
