ClarenceThomas              package:cmm              R Documentation

_O_p_i_n_i_o_n _o_n _S_u_p_r_e_m_e _C_o_u_r_t _n_o_m_i_n_e_e _C_l_a_r_e_n_c_e _T_h_o_m_a_s, _t_w_o-_w_a_v_e _p_a_n_e_l _s_t_u_d_y

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

     Clarence Thomas was nominated in 1991 as member of the U.S.
     Supreme Court by President George H. W. Bush. The nomination
     provoked some public debate because of Clarence Thomas' race
     (black) and because of his allegedly extremely conservative social
     and political views. A panel of U.S.citizens was interviewed
     regarding their opinion on Clarence Thomas' candidacy during
     September 3-5 (A) and on October 9 (B). After the first wave, more
     precisely on September 25, a charge of sexual harassment was
     brought against Clarence Thomas by his former aide, Anita Hill.
     Source: CBS News and New York Times 2001.

     The data are tabulated in Bergsma, Croon, and Hagenaars (2009,
     Table 5.6) and were also used in Bergsma & Croon (2005).

     Section 5.2.1 in Bergsma, Croon, and Hagenaars (2009).

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

     data(ClarenceThomas)

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

     A data frame with 991 observations on the following variables.

     '_A' Opinion on Clarence Thomas during first wave, Sept 3-5, 1991 
          (factor): 1 = Favorable; 2 = Unfavorable; 3 = Undecided; 4 =
          Haven't heard enough;

     '_B' Opinion on Clarence Thomas during second wave, Oct 9, 1991 
          (factor): 1 = Favorable; 2 = Unfavorable; 3 = Undecided; 4 =
          Haven't heard enough;


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

     CBS News and New York Times 2001.

_R_e_f_e_r_e_n_c_e_s:

     Bergsma, W. P., Croon, M. A., & Hagenaars, J. A. P. (2009).
     _Marginal models for dependent, clustered, and longitudinal
     categorical data._ Berlin: Springer

     Bergsma, W. P., & Croon, M. A. (2005). Analyzing categorical data
     by marginal models. In L. A. van der Ark, M. A. Croon, & K.
     Sijtsma (Eds.), _New developments in categorical data analysis for
     the social and behavioral sciences._ Mahwah, NJ: Erlbaum.

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

     data(ClarenceThomas)

     ################################################################
     ## Marginal homogeneity: O1=O2

     # at24 produces vectorized 2x4 table TR (Time x Response)
     at24 <- MarginalMatrix(c("A", "B"), list(c("A"), c("B")), c(4, 4));

     # marginal homogeneity
     bt1 <- ConstraintMatrix(c("T", "R"), list(c("T"), c("R")), c(2, 4));
     model1 <- list(bt1, "log", at24);

     # only first two categories are equated
     bt2 <- rbind(
        c(1, 0, 0, 0,  -1, 0, 0, 0),
        c(0, 1, 0, 0,   0,-1, 0, 0));
     model2 <- c(bt2, "log", at24);

     pi11 <- MarginalModelFit(ClarenceThomas, model1,
         MaxSteps = 500,
         ShowProgress = 20,
         MaxStepSize = .5,
         CoefficientDimensions = c(2, 4),
         Labels = c("T", "R"),
         Title = "Clarence Thomas data, MH");

     ################################################################
     ## Marginal homogeneity: P1=P2
     # P1 and P2 are O1 and O2 conditioned on not being in category 4

     # at24 produces vectorized 2x4 table TR (Time x Response
     at24 <- MarginalMatrix(c("A", "B"), list(c("A"), c("B")), c(4, 4));

     # specify conditional probabilities using generalized exp-log notation
     at1 <- rbind(c(1, 0, 0, 0), c(0, 1, 0, 0), c(0, 0, 1, 0), c(1, 1, 1, 0));
     at1 <- DirectSum(at1, at1);
     at2 <- rbind(c(1, 0, 0, -1), c(0, 1, 0, -1), c(0, 0, 1, -1));
     at2 <- DirectSum(at2, at2);
     coeff <- list(list(diag(6), at2, at1), list("exp", "log", "identity"));

     # marginal homogeneity
     bt1 <- ConstraintMatrix(c("T", "R"), list(c("T"), c("R")), c(2, 3));

     model1 <- list(bt1, coeff, at24);

     pi11 <- MarginalModelFit(ClarenceThomas, model1,
         MaxSteps = 500,
         ShowProgress = 20,
         MaxStepSize = .5,
         CoefficientDimensions = c(2, 3),
         Labels = c("T", "R"),
         Title = "Clarence Thomas data, MH");

