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Weighting data can be done for a number of different reasons, but often to account for sampling bias. 

Weighting can vary from the simple to the complex. You should take care to check weights carefully if you're:

• weighting sub-samples differently from each other
• recomputing weights each time period (wave)
• changing weighting definitions over time

Simple weights can be constructed in the web app, but combining weights will require scripting.

Note: pay attention to whether the weights are being derived automatically or if they are being hard-coded ('materialised') in the data. Weighting can be a tricky part of tracking studies, as it often relies on data collection to be complete before it is implemented.

In the web app

• How to create a weight
• Weighting

Using R

• weight()
• weightVariables() 
• makeWeight()

Crunch Automation

• CREATE WEIGHT command
• SET WEIGHT command