Zależność błędu od głębokości retrospekcji oraz momentu konstrukcji prognozy przy stałym horyzoncie prognozy

The article presents some useful methods for forecasting economical time series with trend and seasonal component. The example concerns milk time series for the years 1993-2000. The prediction was made by the following methods: Winter's exponential smoothing, seasonal decomposition, harmonic analysis, extrapolating a trend of the same stage. The author presented the examination of the methods for the years 1995-2000, which gave satisfactory results - a right forecast highly depends on forecasting methods and number of forecasts. There is relatively weak relationship between the flashback period and the forecast error.