Confidence interval for a ratio of coefficients of variation in a 2-group design

Source: R/statpsych1.R

Computes a confidence interval for a ratio of population coefficients of variation (CV) in a 2-group design. This confidence interval uses the confidence interval for each CV and then uses the MOVER-DL method (see Newcombe, page 138) to obtain a confidence interval for CV1/CV2. The CV assumes ratio-scale scores.

ci.ratio.cv2(alpha, m1, m2, sd1, sd2, n1, n2)

Arguments

alpha

alpha level for 1-alpha confidence

m1

estimated mean for group 1

m2

estimated mean for group 2

sd1

estimated standard deviation for group 1

sd2

estimated standard deviation for group 2

n1

sample size for group 1

n2

sample size for group 2

Value

Returns a 1-row matrix. The columns are:

  • Estimate - estimated ratio of coefficients of variation

  • LL - lower limit of the confidence interval

  • UL - upper limit of the confidence interval

References

Newcombe RG (2013). Confidence Interval for Proportions and Related Measures of Effect Size. CRC Press.

Examples

ci.ratio.cv2(.05, 34.5, 26.1, 4.15, 2.26, 50, 50)
#>  Estimate       LL       UL
#>  1.389188 1.041478 1.854101

# Should return:
# Estimate       LL       UL
# 1.389188 1.041478 1.854101