Answer:
instrumentation
Step-by-step explanation:
Internal Validity
this is the rate of knowing or certainty that a change in the dependent variable (DV) happens or occur due to manipulations. It is the rate at which an experiment is free from extraneous variables.
There are different threats to internal validity. They includes;
1. Maturation
2. History
3. Regression
4. Attrition
5. Testing
6. Instrumentation
Instrumentation threat happens due to only when the pretest and posttest are not sufficiently equivalent. That is simply when the instrument usually called the observers that was used on the posttest and pretest is not the same (differ). This method is what researchers use to test changes over time.