Confidence Bands for the Difference of Two Survival Curves Under Proportional Hazards Model

A common approach to testing for differences between the survival rates of two therapies is to use a proportional hazards regression model which allows for an adjustment of the two survival functions for any imbalance in prognostic factors in the comparison. When the relative risk of one treatment to the other is not constant over time the question of which therapy has a survival advantage is difficult to determine from the Cox model. An alternative approach to this problem is to plot the difference between the two predicted survival functions with a confidence band that provides information about when these two treatments differ. Such a band will depend on the covariate values of a given patient. In this paper we show how to construct a confidence band for the difference of two survival functions based on the proportional hazards model. A simulation approach is used to generate the bands. This approach is used to compare the survival probabilities of chemotherapy and allogeneic bone marrow transplants for chronic leukemia.     

Sexual orientation: a multi-variable dynamic process

Theory and research concerning sexual orientation has been restricted in its scope and influence by the lack of clear and widely accepted definitions of terms like heterosexual, bisexual, and homosexual. In an attempt to better demarcate and understand the complexities of human sexual attitudes, emotions, and behavior, the Klein Sexual Orientation Grid (KSOG) was developed and administered. The KSOG is composed of seven variables that are dimensions of sexual orientation, each of which is rated by the subject as applying to the present, past, or ideal. Analysis of the data from subjects who filled out the KSOG in Forum Magazine indicated that the instrument was a reliable and valid research tool which took into consideration the multi-variable and dynamic aspects of sexual orientation.     

Letter to the Editor: A reply to Zipp and Fenwick

March 2007 In the Fall 2006 issue of Public Opinion Quarterly, John F.Zipp and Rudy Fenwick published "Is the Academy a Liberal Hegemony?,"an article openly framed as a reaction to "right-wing activistsand scholars" (304). The scholarship they cite is principallyours (Klein and Stern 2005a; Klein and Western 2005). They arriveat findings about ideological ratios said to be "far lower thanthe ratios found by Klein ..." (309). Unfortunately, ZF misrepresent us. We wrote and submitted afull reply, but the Editor Peter Miller asked us to keep to     

Ericksonian hypnosis and strategic interventions for sexual orientation confusion

Erickson's utilization approach provides a model of hypnotic and strategic intervention for persons seeking psychotherapy because of sexual orientation confusion. Case studies outline examples of hypnotic and strategic short-term interventions. These cases include the use of metaphor, utilizing resistances, anchoring, and synesthesia.     

Protectionism: An analysis from project LINK

The LINK system of world trade is used to examine present tendencies toward protectionism. In protectionist scenarios we increase the prices of manufactured imports into 13 LINK-OECD countries by 5, 10, and 20 percent respectively, for 1978–1979. If a country's import equations do not depend significantly on relative price, we impose corresponding quantitative import restrictions of 5, 10, and 20 percent. Smaller OECD countries, developing countries, and socialist countries are assumed to be nonprotectionist in these scenarios. The discrepancies between the values of leading variables in the protectionist scenarios and in a baseline case show the effects of the different degrees of protectionism assumed. The results describe and validate Adam Smith's principles of the gains from free trade.     

Reciprocal Associations Among Maternal and Child Characteristics of At‐Risk Families: A Longitudinal Actor–Partner Interdependence Model

Researchers have found linear associations among maternal and child characteristics. However, family systems theorists suggest that relationships are more complex and family members are interdependent. We used actor–partner interdependence modeling to unravel associations among maternal and child characteristics to predict outcomes in adolescence. We used data from 361 mother–child dyads from the Longitudinal Studies of Child Abuse and Neglect and found both actor and partner effects. Maternal depression and history of victimization were associated with children's later reports of lower mother–adolescent relationship quality. Children's perceptions of relationship quality were also associated with mothers' later depressive symptoms and perceptions of relationship quality. Overall, results highlighted interdependence among mothers and their children over time. We discuss implications for marriage and family therapists.     

Testing a block exchangeable covariance matrix

Testing hypotheses about the structure of a covariance matrix for doubly multivariate data is often considered in the literature. In this paper the Rao's score test (RST) is derived to test the block exchangeable covariance matrix or block compound symmetry (BCS) covariance structure under the assumption of multivariate normality. It is shown that the empirical distribution of the RST statistic under the null hypothesis is independent of the true values of the mean and the matrix components of a BCS structure. A significant advantage of the RST is that it can be performed for small samples, even smaller than the dimension of the data, where the likelihood ratio test (LRT) cannot be used, and it outperforms the standard LRT in a number of contexts. Simulation studies are performed for the sample size consideration, and for the estimation of the empirical quantiles of the null distribution of the test statistic. The RST procedure is illustrated on a real data set from the medical studies.     

A Note on Interpersonal and Communication Skills for IS Professionals: Evidence of Positive Influence

A recent article by Byrd and Turner (2001) reported that interpersonal skills on the part of information systems personnel had a negative influence on the success of systems as measured by competitive advantage. Several reasons were forwarded to account for this unexpected result, including lack of richness in the measure of these skills, the use of strategic success measures, the true complexity of interpersonal relations within an organization, and the sample of CIOs who may have a bias in favor of technical skills. We address these concerns by incorporating a set of communication skills into the interpersonal skills set, sampling users for a different set of stakeholders, and employing a more complex model based on theories of expectation. The results indicate that the impacts of interpersonal skills on system success is not a simple function of the perceived level of the IS staff's skill proficiency but is also determined by the understood expectations of skill requirements.