TY - JOUR
T1 - An N-pact factor for clinical psychological research
AU - Reardon, Kathleen W.
AU - Smack, Avanté J.
AU - Herzhoff, Kathrin
AU - Tackett, Jennifer L.
N1 - Publisher Copyright:
© 2019 American Psychological Association.
PY - 2019/8
Y1 - 2019/8
N2 - Although an emphasis on adequate sample size and statistical power has a long history in clinical psychological science (Cohen, 1992), increased attention to the replicability of scientific findings has renewed focus on the importance of statistical power (Bakker, van Dijk, & Wicherts, 2012). These recent efforts have not yet circled back to modern clinical psychological research, despite the importance of sample size and power in producing a credible body of evidence. As one step in this process of scientific self-examination, the present study estimated an N-pact Factor (the statistical power of published empirical studies to detect typical effect sizes; Fraley & Vazire, 2014) in 2 leading clinical journals (the Journal of Abnormal Psychology [JAP] and the Journal of Consulting and Clinical Psychology [JCCP]) for the years 2000, 2005, 2010, and 2015. Study sample size, as one proxy for statistical power, is a useful focus because it allows comparisons with other subfields and may highlight some of the core methodological differences between clinical and other areas. We found that, across all years examined, the average median sample size in clinical research was 179 participants (175 for JAP and 182 for JCCP). The power to detect a small to medium effect size of .20 is just below 80% for both journals. Although the clinical N-pact factor was higher than that estimated for social psychology, the statistical power in clinical journals is still limited to detect many effects of interest to clinical psychologists, with little evidence of improvement in sample sizes over time.
AB - Although an emphasis on adequate sample size and statistical power has a long history in clinical psychological science (Cohen, 1992), increased attention to the replicability of scientific findings has renewed focus on the importance of statistical power (Bakker, van Dijk, & Wicherts, 2012). These recent efforts have not yet circled back to modern clinical psychological research, despite the importance of sample size and power in producing a credible body of evidence. As one step in this process of scientific self-examination, the present study estimated an N-pact Factor (the statistical power of published empirical studies to detect typical effect sizes; Fraley & Vazire, 2014) in 2 leading clinical journals (the Journal of Abnormal Psychology [JAP] and the Journal of Consulting and Clinical Psychology [JCCP]) for the years 2000, 2005, 2010, and 2015. Study sample size, as one proxy for statistical power, is a useful focus because it allows comparisons with other subfields and may highlight some of the core methodological differences between clinical and other areas. We found that, across all years examined, the average median sample size in clinical research was 179 participants (175 for JAP and 182 for JCCP). The power to detect a small to medium effect size of .20 is just below 80% for both journals. Although the clinical N-pact factor was higher than that estimated for social psychology, the statistical power in clinical journals is still limited to detect many effects of interest to clinical psychologists, with little evidence of improvement in sample sizes over time.
KW - Clinical psychology
KW - Metascience
KW - Power
KW - Replicability
KW - Sample size
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U2 - 10.1037/abn0000435
DO - 10.1037/abn0000435
M3 - Article
C2 - 31368728
AN - SCOPUS:85070923859
VL - 128
SP - 493
EP - 499
JO - Journal of Abnormal Psychology
JF - Journal of Abnormal Psychology
SN - 0021-843X
IS - 6
ER -