Forecasting with Statistics A Practical Guide Forecasting helps teams make better decisions. By using statistics, you quantify what you know, what you don’t know, and how confident you are. This guide offers a simple, practical path from data to forecast and clear communication.
A practical workflow:
Define the question: What do you need to forecast, and by when? Gather reliable data: clean, labeled, and relevant history beats perfect methods. Keep notes about data sources and any changes in collection. Choose a method: simple averages for quick answers, regression when you have predictors, and time-series models for patterns over time. Check assumptions: look for trends, seasonality, stationarity, and outliers. Validate results: split data into training and test sets, or use cross-validation. Compare forecasts by accuracy measures like MAPE or RMSE. Communicate uncertainty: prediction intervals help stakeholders see risk, not just a single number. Example: Suppose you track monthly product sales for two years and want the next three months. A quick approach uses a seasonal naive forecast: take the same month last year and adjust for a seasonal factor. A more robust approach fits a small regression using last month sales and a marketing spend variable. Train both models on the first 21 months, test on the last three, and compare.
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