1. What Is a Seasonal Index? A seasonal index (also called a seasonal component or seasonal factor) is a numerical value that quantifies how a particular time period (e.g., a month, quarter, or week) compares to the average period in a seasonal cycle. It is used to measure and remove seasonal variation – predictable, recurring fluctuations that happen within a fixed period (usually one year).

[ \textAdjusted Index_i = \frac\textRaw Index_i\textMean of Raw Indices ]

(We’ll skip full arithmetic for brevity – but you’d smooth the data.)

Now each index shows the seasonal effect relative to the overall average. Suppose quarterly sales (in $1,000) for two years:

seasonal index
seasonal index
seasonal index

Seasonal Index [repack] Access

1. What Is a Seasonal Index? A seasonal index (also called a seasonal component or seasonal factor) is a numerical value that quantifies how a particular time period (e.g., a month, quarter, or week) compares to the average period in a seasonal cycle. It is used to measure and remove seasonal variation – predictable, recurring fluctuations that happen within a fixed period (usually one year).

[ \textAdjusted Index_i = \frac\textRaw Index_i\textMean of Raw Indices ]

(We’ll skip full arithmetic for brevity – but you’d smooth the data.)

Now each index shows the seasonal effect relative to the overall average. Suppose quarterly sales (in $1,000) for two years: