A researcher becomes aware that the judges he is using to make observations are becoming more proficient at their task. This improvement among the judges might suggest a potential threat to the internal validity of the study. What is the source of this threat?

Instrumentation

Explanation:

Instrumentation internal validity threat:

There are seven instruments internal threat are as follows:

Temporal threat History threat Maturation Attrition Testing

Instrumentation: It is very important for research that the instrument used for the research should be accurate in their measurement because its accuracy will be responsible for the outcomes of the study.

Sampling Regression