How To Find Seasonal Index [extra Quality] -

📌 Example: If January’s average sales are 120 and the overall monthly average is 100, the seasonal index = 1.2 (20% above average).

Collect at least 3–5 years of data for the same period (e.g., monthly or quarterly). how to find seasonal index

Find the average value for each season (e.g., average of all Januaries). 📌 Example: If January’s average sales are 120

Calculate the grand mean of all data points across all periods. how to find seasonal index