4. How do time-series or trend analysis methods differ from causal models? Dene trend, cyclical variation, seasonal

4. How do time-series or trend analysis methods differ from causal models? Define trend, cyclical variation, seasonal variation, and irregular variation. What is the purpose of smoothing the data? Describe several methods of smoothing seasonal variations.

Why are short-term forecasts generally more accurate than long-term forecasts?

Why might a forecast of the GNP be more accurate than a forecast of revenues for a particular model of aircraft?