Journal article
Correlating and predicting psychiatric symptom ratings: Spearmans r versus Kendalls tau correlation
Journal of psychiatric research, Vol.33(2), pp.97-104
1999
DOI: 10.1016/S0022-3956(98)90046-2
PMID: 10221741
Abstract
Simple correlations play a large role in the analysis of psychiatric data. They are used to predict outcome, validate new instruments, establish treatment efficacy and find symptom patterns. Researchers and data analysts often face a question about which correlation coefficient to use in a study but are often unaware of the strengths and weaknesses of the alternative correlation measures. The presence of outliers, nonconstant variance, skewed distributions and unequal
n are common in psychiatric data and this poses severe problems for many classic statistical methods. We compare Pearson, Spearman and Kendalls correlation coefficients using a large sample of subjects with schizophrenia spectrum disorders who were evaluated with 7 different psychiatric rating scales. Samples sizes ranging from 8 to 50 were evaluated using bootstrapping methods. The criteria for evaluation of the correlations were the type I error rates, power, bias and confidence interval width. Pearsons
r did not always control for false positives at the nominal rate and was often unstable. Spearmans
r performed better than Pearsons but provided a biased estimate of the true correlation. Spearmans
r was also difficult to interpret. Our results suggest that Kendalls tau
b has many advantages over Pearsons and Spearmans
r; when applied to psychiatric data, tau
b maintained adequate control of type I errors, was nearly as powerful as Pearsons
r, provided much tighter confidence intervals and had a clear interpretation.
Details
- Title: Subtitle
- Correlating and predicting psychiatric symptom ratings: Spearmans r versus Kendalls tau correlation
- Creators
- Stephan Arndt - Mental Health Clinical Research Center, Department of Psychiatry, University of Iowa, 2911 JPP MHCRC, 200 Hawkins Road, Iowa City, IA 52242, USACarolyn Turvey - Department of Preventive Medicine and Environmental Health, University of Iowa, 2911 JPP MHCRC, 200 Hawkins Road, Iowa City, IA 52242, USANancy C Andreasen - Mental Health Clinical Research Center, Department of Psychiatry, University of Iowa, 2911 JPP MHCRC, 200 Hawkins Road, Iowa City, IA 52242, USA
- Resource Type
- Journal article
- Publication Details
- Journal of psychiatric research, Vol.33(2), pp.97-104
- DOI
- 10.1016/S0022-3956(98)90046-2
- PMID
- 10221741
- NLM abbreviation
- J Psychiatr Res
- ISSN
- 0022-3956
- eISSN
- 1879-1379
- Publisher
- Elsevier Ltd
- Language
- English
- Date published
- 1999
- Academic Unit
- Psychiatry; Epidemiology; Iowa Neuroscience Institute; Biostatistics; Nursing; Injury Prevention Research Center
- Record Identifier
- 9984003414902771
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