What do you think would happen if the researcher was half way through the study and realized they had to make a change in the way the data was collected and in the type of data collected?
This is not as uncommon as it might seem, and I have personally experienced this in my own research. The answer really depends on what problem arose to require the change. To further explain, we need to examine validity and reliability of the data collection.
Validity asks, does the instrument collect the data it is meant to ...
This solution provides a brief discussion of what might happen if a data collection change needs to be made half way through a research project.