Testing Effects

A threat to internal validity

Authors

Affiliations

Nate Yomogida, B.S., SPT

Doctor of Physical Therapy

B.S. in Kinesiology

Chloë Kerstein, B.S., SPT

Doctor of Physical Therapy

B.A. in Neuroscience

A testing effect is the result of a problem with the experimental setup that will create a systematic error in one group and not the other.

For tests without control groups, repeated testing that may influence test outcomes regardless of the intervention such as learning or fatigue

Example

• A study designed to measure shoulder strength following an intervention
• The experimental group receives 3 warm‐up trials prior to testing but the control group does not
• The warmup is not part of the intervention, and therefore creates a testing effect that will overestimate tx effects due to improved performance following the practice/warmup trials