rotarod {coin} | R Documentation |
The endurance time of 24 rats in two groups in a rotating cylinder.
data("rotarod")
A data frame with 24 observations on the following 2 variables.
the endurance time
a factor with levels control
and treatment
.
The 24 rats received a fixed oral dose of a centrally acting muscle relaxant
(treatment
) or a saline solvent (control
). They were placed on a rotating
cylinder and the length of time each rat remains on the cylinder is
measured, up to a maximum of 300 seconds.
The rats were randomly assigned to the control and treatment group.
Note that the empirical variance in the control group is 0 and that the group medians are identical.
This dataset serves as the basis of an comparision of the results of the Wilcoxon-Mann-Whitney test computed by 11 statistical packages in Bergmann et al. (2000). The exact conditional p-value is 0.0373 (two-sided) and 0.0186 (one-sided). The asymptotic two-sided p-value (corrected for ties) is reported as 0.0147.
Reinhard Bergmann, John Ludbrook \& Will P. J. M. Spooren (2000). Different outcomes of the Wilcoxon-Mann-Whitney test from different statistics packages. The American Statistician 54(1), 72–77.
### Wilcoxon-Mann-Whitney Rank Sum Test ### one-sided exact (0.0186) wilcox_test(time ~ group, data = rotarod, alternative = "greater", distribution = "exact") ### two-sided exact (0.0373) wilcox_test(time ~ group, data = rotarod, distribution = "exact") ### two-sided asymptotical (0.0147) wilcox_test(time ~ group, data = rotarod)