University of Rochester

About: University of Rochester is a education organization based out in Rochester, New York, United States. It is known for research contribution in the topics: Population & Laser. The organization has 63915 authors who have published 112762 publications receiving 5484122 citations. The organization is also known as: Rochester University.

Back to the Future: Modeling Time Dependence in Binary Data

Abstract: Since Beck, Katz, and Tucker (1998), the standard method for modeling time dependence in binary data has been to incorporate time dummies or splined time in logistic regressions. Although we agree with the need for modeling time dependence, we demonstrate that time dummies can induce estimation problems due to separation. Splines do not suffer from these problems. However, the complexity of splines has led substantive researchers (1) to use knot values that may be inappropriate for their data and (2) to ignore any substantive discussion concerning temporal dependence. We propose a relatively simple alternative: including t, t 2 , and t 3 in the regression. This cubic polynomial approximation is trivial to implement—and, therefore, interpret—and it avoids problems such as quasi-complete separation. Monte Carlo analysis demonstrates that, for the types of hazards one often sees in substantive research, the polynomial approximation always outperforms time dummies and generally performs as well as splines or even more flexible autosmoothing procedures. Due to its simplicity, this method also accommodates nonproportional hazards in a straightforward way. We reanalyze Crowley and Skocpol (2001) using nonproportional hazards and find new empirical support for the historical-institutionalist perspective.

Testing the ruler with item response theory: increasing precision of measurement for relationship satisfaction with the Couples Satisfaction Index.

Abstract: The present study took a critical look at a central construct in couples research: relationship satisfaction. Eight well-validated self-report measures of relationship satisfaction, including the Marital Adjustment Test (MAT; H. J. Locke & K. M. Wallace, 1959), the Dyadic Adjustment Scale (DAS; G. B. Spanier, 1976), and an additional 75 potential satisfaction items, were given to 5,315 online participants. Using item response theory, the authors demonstrated that the MAT and DAS provided relatively poor levels of precision in assessing satisfaction, particularly given the length of those scales. Principal-components analysis and item response theory applied to the larger item pool were used to develop the Couples Satisfaction Index (CSI) scales. Compared with the MAS and the DAS, the CSI scales were shown to have higher precision of measurement (less noise) and correspondingly greater power for detecting differences in levels of satisfaction. The CSI scales demonstrated strong convergent validity with other measures of satisfaction and excellent construct validity with anchor scales from the nomological net surrounding satisfaction, suggesting that they assess the same theoretical construct as do prior scales. Implications for research are discussed.

Origin and evolution of retroelements based upon their reverse transcriptase sequences.

Abstract: To study the evolutionary relationship of reverse transcriptase (RT) containing genetic elements, a phylogenetic tree of 82 retroelements from animals, plants, protozoans and bacteria was constructed. The tree was based on seven amino acid domains totalling 178 residues identified in all RTs. We have also identified these seven domains in the RNA-directed RNA polymerases from various plus-strand RNA viruses. The sequence similarity of these RNA polymerases to RT suggests that these two enzymes evolved from a common ancestor, and thus RNA polymerase can be used as an outgroup to root the RT tree. A comparison of the genetic organization of the various RT containing elements and their position on the tree allows several inferences concerning the origin and evolution of these elements. The most probable ancestor of current retroelements was a retrotransposable element with both gag-like and pol-like genes. On one major branch of the tree, organelle and bacterial sequences (e.g. group II introns and bacterial msDNA) appear to have captured the RT sequences from retrotransposons which lack long terminal repeats (LTRs). On the other major branch, acquisition of LTRs gave rise to two distinct groups of LTR retrotransposons and three groups of viruses: retroviruses, hepadnaviruses and caulimoviruses.