rotarod                 package:coin                 R Documentation

_R_o_t_a_t_i_n_g _R_a_t_s _D_a_t_a

_D_e_s_c_r_i_p_t_i_o_n:

     The endurance time of 24 rats in two groups in a rotating
     cylinder.

_U_s_a_g_e:

     data(rotarod)

_F_o_r_m_a_t:

     A data frame with 24 observations on the following 2 variables.

     _t_i_m_e the endurance time

     _g_r_o_u_p a factor with levels 'control' and 'treatment'. .in -5 

_D_e_t_a_i_l_s:

     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.

_S_o_u_r_c_e:

     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.

_E_x_a_m_p_l_e_s:

     data(rotarod, package = "coin")

     ### 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)

