The evaluation of the average value of the position coordinate,〈x〉, of a particle moving in a harmonic oscillator potential(V(x)=kx2/2)with a small anharmonic piece(V(x)=−λkx3)is a standard calculation in classical Newtonian mechanics and statistical mechanics where the problem has relevance to thermal expansion. In each case, the calculation is most easily done using a perturbative expansion. In this note, we perform the same computation of〈x〉in quantum mechanics using time-independent perturbation theory and the ladder operator formalism to show how similar results are obtained. We also indicate how a semiclassical calculation using a classical probability distribution can also be used to obtain the same result.