I 've used ARMA model for forecasting stock price, but the raw input data(original stock price) is not stationary, so I use the first order difference of raw data, but the acf and pacf figure shows the first order differential data is the white noise.Doses that mean I should not use ARIMA model to predict the stock price?

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#### Best Answer

"Doses that mean I should not use ARIMA model to predict the stock [returns]?"

No, it means if you do, then you should pick an ARIMA(0,1,0) (for the log price). Assuming that model is true, your predictions will depend heavily on the mean or intercept parameter.

On the other hand, if you do believe that stock returns are "more predictable" then you might look to models that are not in the ARIMA family.