Over 9 days even luck would give us 14.6 blocks. During these specific 9 days we ended up finding 12 (+1 stale) blocks. That's bad luck, but calling it 47% seems a bit extreme.
What would perfectly average mining look like? In a perfectly average world we would be finding 1.x something blocks per day and the CDF would always be 50%, right? And the only thing changing that number would be a change in our pool Thps or a change in the mining difficulty.
CDF is definitely not linear. Seems you can get really close to the limits of the scale but never quite reach them. We can mine the snot out of blocks, seemingly forever, before finding one and be somewhere in the 99.x% CDF. It's close but never quite 100%. A pool (not this one:) could mine for a month before finding a block and the CDF would still only be 99.x% only a little closer to 100%.
And what about the other end of the scale? If you find the next block on the very first hash you try, would this equate to exactly 0% CDF? Thanks