In a time series forecast, future values are derived from what?

• A. Expert opinions
• B. Leading indicators
• C. A trend line drawn on past data
• D. Historical data

Answer: (D)

Future values in a time series forecast come from the historical data. By examining past observations, you uncover patterns like overall direction (trend), repeating seasonal effects, and typical fluctuations. A forecasting model uses those patterns learned from the historical data to project what is likely to happen next. External inputs such as expert opinions or leading indicators aren’t the primary basis for a pure time series forecast. A trend line is derived from past data and helps describe that history, but the forecast itself comes from applying a model to the historical data to extend the observed patterns forward.