May 1st, 2005, 8:27 pm
I don't understand your question. "Stationary" and "ergodic" depend on the definition of the time series. You have given a formula for a particular time value, Y(t), but no clue how this relates to Y(x) for any other time. You don't tell us whether the definition of Y(t) is unconditional or conditional. The only difference between your two formulations is F becomes F(t). That seems to say that in the first series, a random number F is chosen from a Normal distribution and added to Y for all t. In that case the distribution it came from is irrelevant to the time series properties of Y, it is just a constant. If you tell us how the time series is formed, we can help you determine if it is stationary or ergodic.