Group Testing vs. Individual Testing: How Your Testing Environment Is Corrupting Your Baseline Data

The environment in which a baseline test is administered has a measurable, significant impact on data quality. This is not a theoretical concern — it’s been demonstrated empirically in published research.

The evidence

A study by Moser et al. (2011), published in Applied Neuropsychology, found that athletes tested in group settings scored significantly lower on ImPACT composite measures compared to those tested individually. The research from the Journal of Athletic Training (Covassin et al., 2017) that established best practices for ImPACT administration limited testing sessions to no more than 2 student-athletes and 2 test administrators in a closed laboratory — specifically because group testing had been shown to negatively influence performance.

The Onate et al. (2007) study examining BESS administration, published in the rehabilitation measures literature, found significant differences in single-leg foam balance scores when comparing controlled locker room environments to uncontrolled sideline environments — with moderate to large effect sizes (0.53–1.03) on the conditions most relevant to concussion detection.

Why environment matters

The mechanisms are straightforward: in a noisy, crowded environment, athletes are distracted by conversations, phone notifications, movement, and visual stimuli. They may rush through the test to keep pace with peers. They receive less individualized supervision, meaning low effort or confusion goes unnoticed. And the social dynamics of group testing may encourage sandbagging — athletes who see peers not taking the test seriously may follow suit.

Best practices

Best practice for baseline testing environments includes: a quiet, well-lit room separate from athletic facilities; no more than 2–4 athletes testing simultaneously; active supervision by a trained administrator who can observe effort and redirect distracted athletes; phones and electronic devices collected before testing begins; and athletes screened for fatigue, recent exercise, illness, or inadequate sleep. For the broader critique, see the garbage-in-garbage-out problem.

How we handle it

At Headquarters, we maintain strict environmental controls during all baseline sessions. We never test more than 4 athletes simultaneously, and our administrators are trained to monitor engagement and effort throughout the testing process.

Frequently asked questions