R Code to Identify Invalid Qualtrics/MTurk Data

This R code is useful for identifying invalid Qualtrics/MTurk data based on the following pre-registered criteria:

1) Participant has not completed the study on Qualtrics;

2) Participant appears more than once in the same study on Qualtrics;

3) Participant appears on Qualtrics but not on MTurk.

This code is based on CloudResearch but also applicable to Prolific. It does not require any packages and uses simple for-loops and if/else statements, but I am open to suggestions for making it even more beginner-friendly!