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WSCV: Stata module to compute the within-subject coefficient of variation

Author

Listed:
  • Ariel Linden

    (Linden Consulting Group, LLC)

Programming Language

Stata

Abstract

wscv computes the within-subject coefficient of variation (WSCV) among two or more repeated tests or ratings. The WSCV is widely used as a measure of reliability and reproducibility for interval-level (continuous) data in medical and biological science. Quan and Shih (1996) recommend the WSCV as an alternative to the intraclass correlation (ICC) to assess reproducibility of a measurement when the study population is homogeneous. In such cases, the ICC (which relies on between-subject variation) will produce a low estimate, whereas the WSCV is unaffected. wscv uses the "within-subject standard deviation method" for computing WSCV, as described in Bland & Altman (1996). Two alternative computation approaches are the "root mean square method" and "logarithmic method" as described in Bland (2006). All methods appear to produce similar point estimates, but there are various approaches to computing confidence intervals that produce different results. wscv computes confidence intervals based on the delta method (Quan and Shih 1996), but I recommend using the bootstrap as shown in the example below. The smaller the WSCV, the better the reproducibility. Estimates produced by wscv can be multiplied by 100 to provide results as a percentage.

Suggested Citation

  • Ariel Linden, 2023. "WSCV: Stata module to compute the within-subject coefficient of variation," Statistical Software Components S459230, Boston College Department of Economics.
    • Handle: RePEc:boc:bocode:s459230
    Note: This module should be installed from within Stata by typing "ssc install wscv". The module is made available under terms of the GPL v3 (https://www.gnu.org/licenses/gpl-3.0.txt). Windows users should not attempt to download these files with a web browser.
    as

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    File URL: http://fmwww.bc.edu/repec/bocode/w/wscv.ado
    File Function: program code
    Download Restriction: no
    File URL: http://fmwww.bc.edu/repec/bocode/w/wscv.sthlp
    File Function: help file
    Download Restriction: no
    File URL: http://fmwww.bc.edu/repec/bocode/l/lungfunctiomn.dta
    File Function: supplementary data file
    Download Restriction: no
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