Just finished reading a book called "Superforecasting" (recommend). One of the stories it tells is about the CIA division who's job it was to predict the odds of things like "Would the Bay of Pigs be successful". The report assessed the chances as "fair" which Kennedy regarded to be a positive assessment. After the fact, the head of the division asked his staff to assign a percentage to term "fair" and he got answers ranging from 30 to 80 percent. Appalled, the head wanted to establish a standardized scale between words and percentages (Excellent-80 Good-66 Average-50 Fair-33 Poor-20) and was totally rejected by the higher ups. The need for CYA is very powerful. In fact, it apparently was considered a huge breakthrough in the forecasting world that percentages were used in the discussion on the raid that killed Osama.
As for ISIS specifically, even before Paris there was an internal assessment within the administration that they hadn't been as effective in cutting of oil income to ISIS as they thought, so they've made a change in strategy (sorry truck drivers).
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