lrtest                package:epicalc                R Documentation

_L_i_k_e_l_i_h_o_o_d _r_a_t_i_o _t_e_s_t

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

     Likelihood ratio test for objects of class 'glm'

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

     lrtest (model1, model2, print=TRUE)

_A_r_g_u_m_e_n_t_s:

model1, model2: Two models of class "glm" having the same set of
          records and the same type ('family' and 'link')

   print: whether the results will be printed

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

     Likelihood ratio test checks the difference between
     -2*logLikelihood of the two models against the change in degrees
     of freedom using a chi-squared test. It is best applied to a model
     from 'glm' to test the effect of a factor with more than two
     levels. The records used in the dataset for both models MUST be
     the same. The function can also be used with "clogit", which does
     not have real logLikelihood.

_A_u_t_h_o_r(_s):

     Virasakdi Chongsuvivatwong <cvirasak@medicine.psu.ac.th>

_S_e_e _A_l_s_o:

     'glm', 'logLik', 'deviance'

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

     model0 <- glm(case ~ induced + spontaneous, family=binomial, data=infert)
     model1 <- glm(case ~ induced, family=binomial, data=infert)
     lrtest (model0, model1)
     lrtest (model1, model0) # same result
     lrtest (model1, model0) -> a
     a

