Calculate trends and seasonality using time series with regression (e.g., deterministic vs. stochastic trend).

Free CAS MAS-II (Modern Actuarial Statistics II) lesson in Time Series with Constant Variance. 15 min read, ~2,183 words.

Deterministic trend:. Fit by OLS on. Forecast variance stays bounded as horizon grows. Stochastic trend (random walk):. The trend is a cumulative sum of shocks. Forecast variance grows linearly in horizon. Seasonal dummies: add indicator regressors (one season is the baseline) to capture additive seasonality of period. Detrend vs difference...

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