Statistical properties of a turbulent cascade are evaluated by considering the joint probability distribution p(v 1, L 1; v 2, L 2) for two velocity increments v 1, v 2 of different lenght scales L 1, L 2. We present experimental evidence that the conditional probability distribution p(v 2, L 2|v 1, L 1) obeys a Chapman-Kolmogorov equation. We evaluate the Kramers-Moyal coefficients and show that the third and fourth order coefficients vanish. The turbulent cascade is described by a drift and diffusion coefficient and the joint probability distributions obey a Fokker-Planck equation. We calculate the drift and diffusion coefficients and discuss their relationship to universal behaviour in the scaling region of the turbulent cascade.