Skip to content

Seasonal Adjustment

Seasonal Adjustment:

The seasonal adjustment is used in time series analysis to remove a periodic component with the known period from the observed time series. This adjustment is normally performed through the seasonal decomposition of the time series followed by subtraction of the seasonal component from the observed data.

The reason for the seasonal adjustment is that large periodic variations in the time series (explainable by known periodically varying factors) may mask weaker but more important variations, like upward or downward trends.

The “seasonal” here does not necessarily mean the season of the year. Any periodical component with known period may be removed from the time series. For example, the total sales in a supermarket depend on the day of the week. Thus, the periodic component that may be of practical interest has the period 7 days, not a year. Removal of this component from, say, 60 days time series of daily sales revenue, can make the actual time trends clearer.

Browse Other Glossary Entries

Test Yourself

Planning on taking an introductory statistics course, but not sure if you need to start at the beginning? Review the course description for each of our introductory statistics courses and estimate which best matches your level, then take the self test for that course. If you get all or almost all the questions correct, move on and take the next test.

Data Analytics

Considering becoming adata scientist, customer analyst or our data science certificate program?

Analytics Quiz

Advanced Statistics Quiz

Statistics Quiz


Looking at statistics for graduate programs or to enhance your foundational knowledge?

Statistics 1 Quiz

Regression Quiz

Regression Quiz


Entering the biostatistics field? Test your skill here.

Biostatistics Quiz

Advanced Statistics Quiz

Statistics 2 Quiz

Stay Informed

Our Blog

Read up on our latest blogs


Learn about our certificate programs


Find the right course for you

Contact Us

We'd love to answer your questions

Our mentors and academic advisors are standing by to help guide you towards the courses or program that makes the most sense for you and your goals.

300 W Main St STE 301, Charlottesville, VA 22903

(434) 973-7673

By submitting your information, you agree to receive email communications from All information submitted is subject to our privacy policy. You may opt out of receiving communications at any time.