Multiple comparisons. The van der Waerden (Normal Scores)

Source: R/waerden.test.R

A nonparametric test for several independent samples.

waerden.test(y, trt, alpha = 0.05, group = TRUE, main = NULL, console = FALSE)

Arguments

y

Variable response
trt

Treatments
alpha

Significant level
group

TRUE or FALSE
main

Title
console

logical, print output

Value

statistics

Statistics of the model

parameters

Design parameters

means

Statistical summary of the study variable

comparison

Comparison between treatments

groups

Formation of treatment groups

Details

The data consist of k samples of possibly unequal sample size.
The post hoc test is using the criterium Fisher's least
significant difference (LSD).

References

Practical Nonparametrics Statistics. W.J. Conover, 1999

See also

BIB.test, DAU.test, duncan.test, durbin.test, friedman, HSD.test, kruskal, LSD.test, Median.test, PBIB.test, REGW.test, scheffe.test, SNK.test, waller.test, plot.group

Examples


library(agricolae)
# example 1
data(corn)
out1<-with(corn,waerden.test(observation,method,group=TRUE))
print(out1$groups)
#>        score groups
#> 3  1.1234030      a
#> 1  0.3582343      b
#> 2 -0.1703415      c
#> 4 -1.1722899      d
plot(out1)
#> Warning: NAs introduced by coercion
out2<-with(corn,waerden.test(observation,method,group=FALSE))
print(out2$comparison)
#>       difference pvalue signif.        LCL        UCL
#> 1 - 2  0.5285759 0.0202       *  0.0883729  0.9687788
#> 1 - 3 -0.7651686 0.0029      ** -1.2479907 -0.2823465
#> 1 - 4  1.5305242 0.0000     ***  1.0649857  1.9960628
#> 2 - 3 -1.2937445 0.0000     *** -1.7658867 -0.8216022
#> 2 - 4  1.0019484 0.0001     ***  0.5474957  1.4564011
#> 3 - 4  2.2956928 0.0000     ***  1.7998443  2.7915414
# example 2
data(sweetpotato)
out<-with(sweetpotato,waerden.test(yield,virus,alpha=0.01,group=TRUE))
print(out)
#> $statistics
#>      Chisq Df    p.chisq  t.value      MSD
#>   8.409979  3 0.03825667 3.355387 1.322487
#> 
#> $parameters
#>      test name.t ntr alpha
#>   Waerden  virus   4  0.01
#> 
#> $means
#>       yield normalScore      std r  Min  Max   Q25  Q50   Q75
#> cc 24.40000  -0.2328353 3.609709 3 21.7 28.5 22.35 23.0 25.75
#> fc 12.86667  -1.0601764 2.159475 3 10.6 14.9 11.85 13.1 14.00
#> ff 36.33333   0.6885684 7.333030 3 28.0 41.8 33.60 39.2 40.50
#> oo 36.90000   0.6044433 4.300000 3 32.1 40.4 35.15 38.2 39.30
#> 
#> $comparison
#> NULL
#> 
#> $groups
#>         score groups
#> ff  0.6885684      a
#> oo  0.6044433      a
#> cc -0.2328353     ab
#> fc -1.0601764      b
#> 
#> attr(,"class")
#> [1] "group"