FAQ: What does "Error: Unexpected value when using external data source" mean?
When using the "Prompt for Data Set" feature of a sequence, the data set provided must only contain values that are in the actual project Data Source (typically associated with the TRIAL sequence). This error occurs when the data set provided at the start of the experiment contains an unknown value - eg a value not in the original Data Source.

The "Spilt by" property of the TRIAL sequence can be used so that subjects only run a subset trials within the Data Source. For example, the "master" Data Source may contain 12 trials (the "iteration" value) but set the "Split by" filed of the sequence to [4] to run only 4 trials. Then ensure that any data set that is loaded only contains 4 trials, and those trials are all included or "from" the master Data Source.


The RandomizerW.exe program, "Start -> All Programs -> SR Research -> Experiment Builder -> Randomizer" (Windows) or "Applications -> ExperimentBuilder -> Randomizer" (Mac), can be used to perform external trial randomization and generate valid data sets from the "master" Data Source.