cen_signedranktest {NADA2}

Wilcoxcon Signed-Rank test for censored data

Description

Performs a nonparametric Wilcoxon signed-rank test of whether the median difference between two columns of paired censored data equals 0. Uses the Pratt adjustment for pairs of equal or indistinguishable values.

Usage

cen_signedranktest(xd, xc, yd, yc, alternative = "two.sided", printstat = TRUE)

Arguments

xd

The first column of data values plus detection limits

xc

The column of censoring indicators for xd, where 1 (or TRUE) indicates a detection limit in the xd column, and 0 (or FALSE) indicates a detected value in xd.

yd

The second column of data values plus detection limits, or a single number representing a standard / guideline value.

yc

The column of censoring indicators for yd, where 1 (or TRUE) indicates a detection limit in the yd column, and 0 (or FALSE) indicates a detected value in yd. Not needed if yd is a single standard number.

alternative

The usual notation for the alternate hypothesis. Default is ⁠“two.sided”⁠. Options are ⁠“greater”⁠ or ⁠“less”⁠.

printstat

Logical TRUE/FALSE option of whether to print the resulting statistics in the console window, or not. Default is TRUE.

Value

Prints a list of Wilcoxon Signed-Rank test with Pratt correction for ties statistics containing the following components:

• n Number of samples

• Z The value of the test statistic

• p.value the p-value of the test

References

Helsel, D.R., 2011. Statistics for censored environmental data using Minitab and R, 2nd ed. John Wiley & Sons, USA, N.J.

Page, E.B., 1963. Ordered Hypotheses for Multiple Treatments: A Significance Test for Linear Ranks. Journal of the American Statistical Association 58, 216–230. doi: 10.2307/2282965

Pratt, J.W., 1959. Remarks on Zeros and Ties in the Wilcoxon Signed Rank Procedures. Journal of the American Statistical Association 54, 655–667. doi: 10.2307/2282543

Examples

data(atrazine)

cen_signedranktest(atrazine$June,atrazine$JuneCen,atrazine$Sept,atrazine$SeptCen)