Multiple correlations and Bonferroni's correction

Biol Psychiatry. 1998 Oct 15;44(8):775-7. doi: 10.1016/s0006-3223(98)00043-2.


Correlation coefficients between biological measurements and clinical scales are often calculated in psychiatric research. Calculating numerous correlations increases the risk of a type I error, i.e., to erroneously conclude the presence of a significant correlation. To avoid this, the level of statistical significance of correlation coefficients should be adjusted. Threshold levels of significance for correlation coefficients were adjusted for multiple comparisons in a set of k correlation coefficients (k = 1, 5, 10, 20, 50, 100) by Bonferroni's correction. Significant correlation coefficients were then calculated according to sample size. The change in the threshold values of significance is larger when the number of correlations goes from 1 to 5 than when it goes from 50 to 100. A correlation coefficient, statistically significant at 5% when calculated alone, can be under the threshold level of significance when calculated even among a few other coefficients. Focusing on the most relevant variables or the use of multivariate statistics is advocated.

MeSH terms

  • Data Interpretation, Statistical*
  • Psychiatric Status Rating Scales
  • Psychiatry / statistics & numerical data*
  • Research Design
  • Sample Size