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CPS2204 T. von R. et al.

                      The   ̂  is  a  diagnostic  measure  for  assessing  the  simultaneous
                               ,
                                                                                 ̂
                  influence  of  several  observations  on  the  parameter  estimates, .  Since  all
                  parameters in the model are estimated from the perturbed model,  ̂  is
                                                                                        ,
                  regarded to be a joint-parameter influence measure. It can be of interest to
                  assess  the  influence  of  multiple  observations  on  a  particular  parameter
                            ̂
                  estimate,   , in model (1). If this is the case, we use the same methodology as
                            
                  above and obtain a marginal-parameter influence measure.

                              ̂
                           ̂
                      ̂
                  Let  = ( ,  )be a vector of parameter estimates, where
                               
                            1
                                                ̂
                                         ̂
                                                                  ̂
                                          = ( , . . . ,  ̂ −1 ,  ̂ +1 , … ,  ),
                                                 1
                                                                   
                                           1

                  are the maximum likelihood estimates from the unperturbed model (1), and
                  ̂
                    is estimated from the perturbed model (11).
                   

                  References
                  1.  R.D. Cook, Assessment of local inuence, J. R. Stat. S. Ser. B 48 (1986), pp.
                      133{169.
                  2.  D.A. Belsley, E. Kuh, and R.E. Welsch, (1980), Regression Diagnostics:
                      Identifying Inuential Data and Sources of Collinearity, New York: John
                      Wiley.
                  3.  N. Billor and R.M. Loynes Local inuence: A new approach, Comm. Statist-
                      Theory Meth. 22 (1993), pp. 1595{1611.
                  4.  R.D. Cook Detection of inuential observations in linear regression,
                      Technometrics 19 (1977), pp. 15{18. R.D. Cook Inuential observations in
                      linear regression, J. Amer. Statist. Assoc. 74 (1979), pp. 169{174.
                  5.  R.D. Cook and S. Weisberg (1982). Residuals and Inuence in Regression.
                      New York: Chapman and Hall.
                  6.  B. Efron and R.J. Tibshirani (1993). An Introduction to Bootstrap. New
                      York: Chapman and Hall.
                  7.  FUNG, W. K. (1993). Unmasking outliers and leverage points: a
                      con_rmation. Jour. Amer. Statist. Assoc. 88, 515-519. A.S. Hadi and J.S.
                      Simonoff Procedures for the identi_cation of multiple outliers in linear
                      models, Jour. Amer. Statist. Assoc 88 (1993), pp. 1264{1272.
                  8.  A.J. Lawrance Regression transformation diagnostic using local inuence,
                      Jour. Amer. Statist. Assoc. 83 (1990), pp. 1067{1072.
                  9.  P. Prescott An approximation test for outliers in linear models,
                      Technometrics 17 (1975), 129{132.
                  10. S. Weisberg (1985). Applied Linear Regression. 2nd. Ed. New York: Wiley







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