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Type: Package
Title: Tests for the Equality of Coefficients of Variation from Multiple Groups
Version: 0.2.0
Maintainer: Ben Marwick <benmarwick@gmail.com>
Description: Contains functions for testing for significant differences between multiple coefficients of variation. Includes Feltz and Miller's (1996) <doi:10.1002/(SICI)1097-0258(19960330)15:6%3C647::AID-SIM184%3E3.0.CO;2-P> asymptotic test and Krishnamoorthy and Lee's (2014) <doi:10.1007/s00180-013-0445-2> modified signed-likelihood ratio test. See the vignette for more, including full details of citations.
License: MIT + file LICENSE
Encoding: UTF-8
LazyData: true
RoxygenNote: 6.1.1
Suggests: knitr, ggplot2, rmarkdown, testthat, dplyr, tidyr, ggbeeswarm, covr
VignetteBuilder: knitr
URL: https://github.com/benmarwick/cvequality
BugReports: https://github.com/benmarwick/cvequality/issues
Date: 2019-01-05
NeedsCompilation: no
Packaged: 2019-01-07 07:30:25 UTC; rstudio-user
Author: Ben Marwick [aut, cre], Kalimuthu Krishnamoorthy [aut]
Repository: CRAN
Date/Publication: 2019-01-07 15:10:02 UTC

LRT_STAT, required by mlrt_test

Description

LRT_STAT, required by mlrt_test

Usage

LRT_STAT(n, x, s, seed)

Arguments

n

... as above

x

...

s

...

seed

optional, an integer that is the starting point used in the generation of a sequence of random numbers. Include a seed if you want reproducible output.

Value

xx


Asymptotic test for the equality of coefficients of variation from k populations, using measurement data

Description

Test for k samples (k sample populations with unequal sized) from Feltz CJ, Miller GE (1996) An asymptotic test for the equality of coefficients of variation from k population. Stat Med 15:647–658

Usage

asymptotic_test(x, y, seed)

Arguments

x

a numeric vector containing individual measurement values

y

a vector of any type containing a grouping variable

seed

optional, an integer that is the starting point used in the generation of a sequence of random numbers. Include a seed if you want reproducible output.

Value

a list with the test statistic and p-value

Examples


 y <- unlist(lapply(letters[1:5], function(i) rep(i, 20)))
 x <- rnorm(100)

 asymptotic_test(x, y)


Asymptotic test for the equality of coefficients of variation from k populations, using summary statistics when raw measurement data are not available.

Description

Test for k samples (k sample populations with unequal sized) from Feltz CJ, Miller GE (1996) An asymptotic test for the equality of coefficients of variation from k population. Stat Med 15:647–658

Usage

asymptotic_test2(k, n, s, x, seed)

Arguments

k

a numeric vector the number of groups

n

a numeric vector the numer of measurements in each group

s

a numeric vector the standard deviation of each group

x

a numeric vector the mean of each group

seed

optional, an integer that is the starting point used in the generation of a sequence of random numbers. Include a seed if you want reproducible output.

Value

a list with the test statistic and p-value

Examples


# Summary stats from Feltz and Miller 1996

miller <- data.frame(test = c('ELISA', 'WEHI', '`Viral inhibition`'),
                    Mean = c(6.8, 8.5, 6.0),
                    CV =   c(0.090, 0.462, 0.340),
                    N =    c(5, 5, 5))
# compute SD from mean and cv
miller$SD <- with(miller, CV * Mean)

 asymptotic_test2(k = nrow(miller), n = miller$N, s = miller$SD, x = miller$Mean)


Modified signed-likelihood ratio test (SLRT) for equality of CVs, using measurement data

Description

Modified signed-likelihood ratio test (SLRT) for equality of CVs, using measurement data

Usage

mslr_test(nr = 1000, x, y, seed)

Arguments

nr

numeric vector length one, number of simulation runs, default is 1e3

x

a numeric vector containing individual measurement values

y

a vector of any type containing a grouping variable

seed

optional, an integer that is the starting point used in the generation of a sequence of random numbers. Include a seed if you want reproducible output.

Value

a list with the test statistic and p-value

References

http://link.springer.com/article/10.1007/s00180-013-0445-2 Krishnamoorthy, K. & Lee, M. Comput Stat (2014) 29: 215. doi:10.1007/s00180-013-0445-2

Examples


 x <- rnorm(100)
 y <- unlist(lapply(letters[1:5], function(i) rep(i, 20)))

 mslr_test(nr = 1e3, x, y)



# Modified signed-likelihood ratio test (SLRT) for equality of CVs, using summary statistics when raw measurement data are not available.

Description

# Modified signed-likelihood ratio test (SLRT) for equality of CVs, using summary statistics when raw measurement data are not available.

Usage

mslr_test2(nr, n, x, s, seed)

Arguments

nr

numeric vector lenght one, number of simulation runs

n

a numeric vector, the number of observations in each group

x

a numeric vector, the mean of each group

s

a numeric vector, the standard deviation of each group

seed

optional, an integer that is the starting point used in the generation of a sequence of random numbers. Include a seed if you want reproducible output.

Value

a list with the test statistic and p-value

References

http://link.springer.com/article/10.1007/s00180-013-0445-2

Examples


# Summary stats from Feltz and Miller 1996

miller <- data.frame(test = c('ELISA', 'WEHI', '`Viral inhibition`'),
                    Mean = c(6.8, 8.5, 6.0),
                    CV =   c(0.090, 0.462, 0.340),
                    N =    c(5, 5, 5))
# compute SD from mean and cv
miller$SD <- with(miller, CV * Mean)

 mslr_test2(nr = 1e3, n = miller$N, s = miller$SD, x = miller$Mean)


These binaries (installable software) and packages are in development.
They may not be fully stable and should be used with caution. We make no claims about them.
Health stats visible at Monitor.