Trend, seasonality and noise

Simple forecasting methods remain useful when their fit and limits are understood. This primer explains trend, seasonality and noise with a planner’s workflow in mind.

Practitioner lens

For trend, seasonality and noise, inspect the history for stockouts, promotions, calendar changes and missing periods. Observed sales can differ from the demand customers actually wanted.

First experiment

Draw the series before fitting a model; mark missing periods, stockouts, promotions and calendar changes.

This is an original educational brief. It is a starting point for discussion, not a claim that one technique fits every supply chain.