Explaining Uncertainty in UK Intelligence Assessment

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   Probability says how likely the event is; confidence says how solid the basis for saying so is. They are two axes and are written separately.

   Explaining Uncertainty in UK Intelligence Assessment · 2025

   Missing evidence lowers confidence, not probability.

   These are two different questions: how likely the event is, and how solid your basis for saying so is. You can judge an attack likely on the strength of a single new source — high probability, low confidence — or unlikely on ten years of consistent data — low probability, high confidence. The British guidance grades analytical confidence (the Analytical Confidence Rating) as one of three levels — high, moderate, low — against three criteria: information base, analytical rigour, and complexity and volatility. Confidence also tells the reader how easily the judgement might change. The practical rule: express probability with a word from the scale, and explain confidence separately, with its reason — which source is missing, what could change the picture. ICD 203 goes down to grammar: a product using a confidence level must not combine it with a degree of likelihood in the same sentence. The reason is a phrase such as we have high confidence that it is unlikely, which the reader hears as a single number. The trap: lowering the probability when what you really lack is evidence. Missing evidence lowers confidence; it does not automatically move the event towards unlikely.

   “Whereas probability reflects the likelihood that a statement is true, analytical confidence reflects the soundness and stability of the foundations on which the assessment of likelihood has been made.”

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