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How many is enough? Determining optimal sample sizes for normative studies in pediatric neuropsychology

Ana J Bridges1, Karen A Holler

  • 1Department of Psychology, University of Rhode Island, Kingston, RI, USA. abri7799@postoffice.uri.edu

Child Neuropsychology : a Journal on Normal and Abnormal Development in Childhood and Adolescence
|September 14, 2007
PubMed

Insights

Pediatric neuropsychological norms require adequate sample sizes to ensure accurate confidence intervals (CIs). Optimal sample sizes of 50-75 participants per cell prevent overpathologizing and justify research costs.

Area of Science:

  • Neuropsychology
  • Psychometrics
  • Biostatistics

Background:

  • Pediatric neuropsychological norms are essential for interpreting test results in children.
  • Confidence intervals (CIs) quantify the uncertainty around these norms.
  • The impact of sample size on the reliability of these CIs is not fully understood.

Purpose of the Study:

  • To examine how confidence intervals (CIs) for pediatric neuropsychological norms are affected by sample size.
  • To identify optimal sample sizes for conducting pediatric normative studies.

Main Methods:

  • Calculated 95% CIs for existing pediatric norms across four common neuropsychological instruments.
  • Simulated CIs across a range of sample sizes (n=5 to n=500).

Main Results:

  • Some existing pediatric norms exhibit unacceptably wide CIs.
  • Wider CIs were observed with smaller sample sizes, increasing the risk of overpathologizing.
  • Optimal sample sizes were determined to be between 50 and 75 participants per cell.

Conclusions:

  • Normative studies in pediatric neuropsychology should aim for sample sizes of 50-75 participants per cell.
  • Insufficient sample sizes can lead to inaccurate interpretations and overpathologizing of results.
  • Larger sample sizes beyond this range may not offer proportional benefits to justify the increased costs.

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