Final answer:
The four confounding threats to internal validity are limitations of the measuring device, skill of the measurer, irregularities in the object being measured, and any other situational factors affecting the outcome.
Step-by-step explanation:
The four confounding threats to internal validity include:
- Limitations of the measuring device.
- The skill of the person making the measurement.
- Irregularities in the object being measured.
- Any other factors that affect the outcome (highly dependent on the situation).
Confounding occurs when an experimenter is unable to differentiate the effects that different factors have on their study's outcome. For example, if a student has a high score on an exam, it is challenging to isolate whether it was due to the increased study time or sitting in their favorite spot, as both factors could have influenced the result. To reduce the effects of confounding variables and increase internal validity, experimental designs often include random assignment of subjects to treatment groups and a control group to compare against the effect of the treatment.