Let (Xt ) be a diffusion on the interval (l,r) and Δn a sequence of positive numbers tending to zero. We define J i as the integral between iΔn and (i + 1)Δn of X s .We give an approximation of the law of (J0,...,Jn-1)by means of a Euler scheme expansion for the process (Ji ). In some special cases, an approximation by anexplicit Gaussian ARMA(1,1) process is obtained.When Δn = n-1 we deduce from this expansion estimatorsof the diffusion coefficient of X based on (Ji ). These estimatorsare shown to be asymptotically mixed normal as n tends to infinity.
