In a survey, I used a measurement of uncertainty as a key dependent variable, and after implementing the measurement in 2 waves of my survey, I found a better measurement and this new measurement has better internal validity and fits better theoretically. I still have 2 waves of survey to be sent and I want to add the new measurement.
How to proceed with the analysis? I will likely have 2 waves of data with the old measures, and 2 waves with both the old and the new measures. The waves of data are just batches of sampling, but it seems all 4 waves are needed to have a good enough sampling size.