Well, that depends on if it's a normal distribution or not! 🙂
But I think I know what you mean hear, so here's an example using LEN from my cheapie Firewall at home. Now, because LEN is really all over the place but I know there's LOTS of DNS requests in the 40-75 byte range, when LEN is under 100 I would expect to see a bell-curve like chart. (Or something near enough for demonstration purposes).
| bin LEN
| stats count by LEN
Which gives me
Now for your needs you didn't provide an actual search to go off of, but you could try pretty much what I did only replace LEN with time_taken.
<your base search>
| bin bins=100 time_taken
| stats count by time_taken
You'll notice I also bumped up the number of bins it can make - it won't MAKE 100 bins unless it finds a reason to, but I've told it that it COULD make up to 100 bins.