The probability of a block being solved after 10 minutes: 50%, or 1/2
I might be doing something wrong, but it seems my data shows that 65% of block have been solved in less than 10 minutes. The difference seems a bit too large to be explained by our "faster mining", no?
No, the probability after 10 minutes at constant hashrate would approach, IIRC, 1 - exp(-1), not 50%. The
average time would be 10 minutes, but not the
median as 50% would imply. The long tail at the high end pulls the average above the median.
1-exp(-1) is c. 63%, a little less than your number, as one would expect given the history of increasing network speed.