|Just how did the CIA, NSA, DoD agencies, etc. estimate the CEP of Soviet ballistic missiles? It's not as if the Strategic Rocket Forces would paint a giant bullseye in Kamchatka; the US could certainly observe the launches and monitor the telemetry, but this doesn't necessarily lead to knowing that the warhead was meant to hit (x,y) and landed (z) kilometers away. To what extent was the CEP estimation based strictly on guesswork?
You may recall that supposed improvements in Soviet ICBM CEP were hailed in the 70s and 80s as a major threat to US ICBMs, leading to the whole MX, Midgetman, etc. business.