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Confidence interval for a coefficient of dispersion

Source: R/statpsych1.R
ci.cod.Rd

Computes a confidence interval for a population coefficient of dispersion (COD). The COD is a mean absolute deviation from the median divided by the median. The coefficient of dispersion assumes ratio-scale scores and is a robust alternative to the coefficient of variation (see ci.cv). An approximate standard error is recovered from the confidence interval.

For more details, see Section 1.27 of Bonett (2021, Volume 1)

Usage

ci.cod(alpha, y)

Arguments

alpha

alpha level for 1-alpha confidence

y

vector of scores

Value

Returns a 1-row matrix. The columns are:

  • Estimate - estimated coefficient of dispersion

  • SE - recovered standard error

  • LL - lower limit of the confidence interval

  • UL - upper limit of the confidence interval

References

Bonett DG, Seier E (2006). “Confidence interval for a coefficient of dispersion in nonnormal distributions.” Biometrical Journal, 48(1), 144–148. ISSN 0323-3847, doi:10.1002/bimj.200410148 .

Bonett DG (2021). Statistical Methods for Psychologists https://dgbonett.sites.ucsc.edu/.

Examples

y <- c(30, 20, 15, 10, 10, 60, 20, 25, 20, 30, 10, 5, 50, 40,
       20, 10, 0, 20, 50)
ci.cod(.05, y)
#>   Estimate        SE        LL       UL
#>  0.5921053 0.1814708 0.3813259 1.092679

# Should return:
#  Estimate        SE        LL       UL
# 0.5921053 0.1814708 0.3813259 1.092679