Tonight, Matt Garza pitched the fifth no-hitter of 2010. He joins Edwin Jackson, Roy Halladay, Dallas Braden, and Ubaldo Jimenez in the Year of the Pitcher club.
As I pointed out when Jackson hit his no-hitter, no-hit games are probably Poisson distributed. Let’s update the chart.
The Poisson distribution has probability density function
Maintaining our prior rate of 2.45 no-hitters per season, that means 
The probabilities remain the same:
| n | p | cumulative |
| 0 | 0.0863 | 0.0863 |
| 1 | 0.2114 | 0.2977 |
| 2 | 0.2590 | 0.5567 |
| 3 | 0.2115 | 0.7683 |
| 4 | 0.1296 | 0.8978 |
| 5 | 0.0635 | 0.9613 |
| 6 | 0.0259 | 0.9872 |
| 7 | 0.0091 | 0.9963 |
| 8 | 0.0028 | 0.9991 |
| 9 | 0.0008 | 0.9998 |
| 10 | 0.0002 | 1.0000 |
And though the expectation (E(49)) and cumulative expectation (C(49)) remain the same, the observed values shift slightly:
| E(49) | Observed | C(49) | Total |
| 4.23 | 5 | 4.23 | 5 |
| 10.36 | 11 | 14.59 | 16 |
| 12.69 | 8 | 27.28 | 24 |
| 10.36 | 17 | 37.65 | 41 |
| 6.35 | 1 | 43.99 | 42 |
| 3.11 | 5 | 47.10 | 47 |
| 1.27 | 1 | 48.37 | 48 |
| 0.44 | 0 | 48.82 | 48 |
| 0.14 | 1 | 48.95 | 49 |
| 0.04 | 0 | 48.99 | 49 |
| 0.01 | 0 | 49.00 | 49 |
The tailing observations (say, for 4+ no-hitters) don’t quite match the expected frequencies, but the cumulative values match quite nicely. There might be some unobserved variables that explain the weirdness in the upper tail. Still, cumulatively, we have 47 seasons with 5 or fewer no-hitters, which is almost exactly what’s expected. This is unusual, but not outside the realm of statistical expectation.
