Do you have questions not answered here? Please send suggestions for other questions to "faq" at catherinechhood.net.

Please also see the Seasonal Adjustment Glossary.

- What is a time series?
- What is seasonal adjustment?
- What kind of data do we need for seasonal adjustment?
- Why seasonally adjust data?
- How much data do I need to get a reasonable adjustment?
- What are the components of a time series decomposition?
- What effects are removed during seasonal adjustment?
- What is an ARIMA model?
- What is a regARIMA model?
- How do I generate a seasonally adjusted series?
- What are seasonal filters?
- What are trend filters?
- Why do the seasonal factors change when new data is added?
- How do I choose between additive and a multiplicative models?
- What is an indirect (or a direct) adjustment? Why would I need one?

- What is X-12-ARIMA and X-13ARIMA-SEATS?
- How do I get a copy of X-12-ARIMA or X-13ARIMA-SEATS?
- How do I run X-12-ARIMA and/or X-13ARIMA-SEATS?
- How do I find what I need from the output file?
- How do I save output into Excel?
- How does X-12-ARIMA estimate the trend and seasonal components?
- How does X-12-ARIMA estimate the trading day and moving holiday components?
- What seasonal filters are available in X-12-ARIMA?
- What trend filters are available in X-12-ARIMA?
- How does X-12-ARIMA handle extreme values or outliers?
- What if I have a holiday not included in X-12-ARIMA?
- How do I process a large number of series?
- How do I get X-12-ARIMA to calculate an adjustment for the total of my series?
- How do I get updates and/or more information on X-12-ARIMA?
- Is there training available?
- How do I get started?
- Can I run X-12-ARIMA from Excel?
- What is new in X-13ARIMA-SEATS?
- Why should I switch to X-13ARIMA-SEATS?
- How do I know if ARIMA-model-based adjustments are right for my series?

- What is TRAMO/SEATS?
- How do I get a copy of TRAMO/SEATS?
- How do I run TRAMO/SEATS?
- Can I run TRAMO/SEATS from Excel?
- How does TRAMO/SEATS estimate the trend and seasonal components?
- How does TRAMO/SEATS estimate the trading day and moving holiday components?
- How does TRAMO/SEATS handle outliers?
- How do I get more information? Is there training available?
- How do I get started?

- What are the features of a quality seasonal adjustment?
- What diagnostics are available in X-12-ARIMA (and X-13) to help us judge the quality of the adjustment?
- What do I do if the diagnostics fail?
- How do I "fix" failing M diagnostics?
- How much data do I need to get diagnostics information from X-12-ARIMA?

- What do I do if I can't get X-12-ARIMA to run?
- What do I do if I can't get X-12/X-13 installed?
- How can I get X-12-ARIMA to run for my short series?
- How can I get X-12-ARIMA to run for my weekly series?
- What do I do if I click on a spec file and I get an error message?

Page design by David Joyce

FAQ written by Catherine C.H. Hood

with help from Lynn Imel, Kathy McDonald-Johnson, David Findley, Brian Monsell, and James Ashley

Copyright 2006-2015

Last modified: 19 April 2015