Group Size Effects for Baseline and Post-Injury Sports-Related Concussion

1. Group Size Effects for Baseline and Post-Injury Sports-Related Concussion Melissa N. Womble, Martin L. Rohling, Benjamin D. Hill, & Emily R. Corley Combined-Integrated Clinical and Counseling Psychology Program, University of South Alabama, Mobile, AL 36688 Purpose The purpose of this study is to examine group size effects when collecting baseline data on two computerized neuropsychological screening batteries. Research has suggested that group testing may create group inter-distraction, motivational impairment, or carelessness. Findings will help clinicians better understand group size effects in order to collect the most valid and reliable baseline data and appropriately utilize this data when making return-to-play decisions . Method Immediate Postconcussion Assessment and Cognitive Testing (ImPACT) and Concussion Vital Signs (CVS) were used to measure aspects of cognitive functioning. Participants were 1757 high school and college student athletes and college student controls who completed CVS and 1164 high school and college students and college student controls who completed ImPACT during baseline in small group sizes (one to three student athletes) or large group sizes (seven to twenty student athletes). Average group size in the small group size was 2.45 (SD = 1.61) and in the large group size was 19.42 (SD = 6.04). Figures Immediate Postconcussion Assessment and Cognitive Test Results There was not a statistically significant effect of group size on the overall test battery mean (OTBM) for ImPACT (F(1, 1161) = 1.56 , p = .21) but was a statistically significant effect for CVS (F(1, 1753) = 12.24, p = .0005).OTBMsfor ImPACT were: (Small Group Size = 96.13) and (Large Group Size = 93.28). OTBMs for CVS were: (Small Group Size = 95.32) and (Large Group Size = 91.04). On the individual domains for ImPACT a significant difference was found for reaction time (p = .01). On the individual domains for CVS significant differences were seen on reaction time (p = .03), complex attention (p = .006), cognitive flexibility (p = .0009), processing speed (p < .0001), and executive function (p = .0002). Correlations between the OTBM for ImPACT and CVS were .63. Additional analyses utilizing an experimental logistical regression performance validity formula for CVS found that 15.5% of participants performed invalidly, specifically 1% performed invalidly in the small group size and 14. 6% performed invalidly in the large group size. Utilizing a second experimental embedded performance validity measure for CVS based on performance 2 SDs below the mean 14.1% of participants performed invalidly, specifically 9.2% in the small group size and 14.6% in the large group size. The embedded validity indicator used by ImPACT found that 1.5% of participants performed invalidly, specifically 2.2% in the small group size and 1.4% in the large group size. Concussion Vital Signs DiscussioN ANOVA results revealed that the overall test battery mean and several individual domain scores for CVS varied significantly by group size. A similar pattern was observed for ImPACT, however, results for the OTBM were not statistically significant. Additional analyses of experimental performance validity measures for CVS suggest that a greater number of participants performed invalidly in the large group size. Results suggest that it may not be appropriate to compare results from athletes tested in large group sizes during baseline and small group sizes during post-injury testing. Additional research is needed for performance validity measures when utilizing computerized testing batteries. Citation: Womble, M. N., Rohling, M. L., Hill, B. D., & Corley, E. R. (2012, November). Group size effects for baseline and post-injury sports-related concussion. Poster presented at the annual meeting of the National Academy of Neuropsychology (NAN), Nashville, TN. Email Addresses: meliss0625@hotmail.com and mrohling@usouthal.edu