I just accessed the CME FedWatch Tool at 10:27am ET.
It reported mid price of ZQZ2 as 95.8788 and a corresponding probability of 74.7% of 50bp hike at Dec FOMC meting (vs 75bp).
For December, as this question explains, there are 14 days of effective Fed funds rate at 3.83% and 17 days of EFFR to be decided at the Dec 14 FOMC meeting.
The implied probability should be (futures MID - weighted EFFR)/(size of hike * num of days after hike/total), which, for 50bp, is (95.8788 - 95.6216)/(0.5 * 17/31) and that's 93.8%.
Why is there such a large difference between what should make intuitive sense and the CME FedWatch Tool number?
Btw, when I accessed the page earlier, it reported the same probability for a different ZQZ2 mid of 95.8738. How can that be?