Let \((\Omega, S, P)\) be a probability space and \(A \in S\) an event with its indicator function \(1_ A\). It is well-known that the conditional probability with respect to a subfield \(G \subset S\) satisfies \(P(A \mid G) = 1_ A\) if \(A \in G\) and that \(P(A \mid G)\) is a general function on [0,1] if \(A\) is not measurable with respect to \(G\). Therefore, the author considers \(P(A \mid G)\) as a fuzzy set with the interpretation that \(P(A\mid G)\) is the result of observing \(A\) with respect to the subfield \(G\). Using the fuzzy entropy measure of De Luca and Termini the author proves that \(P(A \mid G)\) becomes fuzzier as \(G\) becomes coarser. The same holds if \(A\) is a fuzzy event.