Examining DIF in the Context of CDMs When the Q-Matrix Is Misspecified.

The rise in popularity and use of cognitive diagnostic models (CDMs) in educational research are partly motivated by the models' ability to provide diagnostic information regarding students' strengths and weaknesses in a variety of content areas. An important step to ensure appropriate interpretations from CDMs is to investigate differential item functioning (DIF). To this end, the current simulation study examined the performance of three methods to detect DIF in CDMs, with particular emphasis on the impact of Q-matrix misspecification on methods' performance. Results illustrated that logistic regression and Mantel-Haenszel had better control of Type I error than the Wald test; however, high power rates were found using logistic regression and Wald methods, only. In addition to the tradeoff between Type I error control and acceptable power, our results suggested that Q-matrix complexity and item structures yield different results for different methods, presenting a more complex picture of the methods' performance. Finally, implications and future directions are discussed.

A global optimization algorithm inspired in the behavior of selfish herds.

In this paper, a novel swarm optimization algorithm called the Selfish Herd Optimizer (SHO) is proposed for solving global optimization problems. SHO is based on the simulation of the widely observed selfish herd behavior manifested by individuals within a herd of animals subjected to some form of predation risk. In SHO, individuals emulate the predatory interactions between groups of prey and predators by two types of search agents: the members of a selfish herd (the prey) and a pack of hungry predators. Depending on their classification as either a prey or a predator, each individual is conducted by a set of unique evolutionary operators inspired by such prey-predator relationship. These unique traits allow SHO to improve the balance between exploration and exploitation without altering the population size. To illustrate the proficiency and robustness of the proposed method, it is compared to other well-known evolutionary optimization approaches such as Particle Swarm Optimization (PSO), Artificial Bee Colony (ABC), Firefly Algorithm (FA), Differential Evolution (DE), Genetic Algorithms (GA), Crow Search Algorithm (CSA), Dragonfly Algorithm (DA), Moth-flame Optimization Algorithm (MOA) and Sine Cosine Algorithm (SCA). The comparison examines several standard benchmark functions, commonly considered within the literature of evolutionary algorithms. The experimental results show the remarkable performance of our proposed approach against those of the other compared methods, and as such SHO is proven to be an excellent alternative to solve global optimization problems.

Parameter Recovery in Multidimensional Item Response Theory Models Under Complexity and Nonnormality.

Information about the psychometric properties of items can be highly useful in assessment development, for example, in item response theory (IRT) applications and computerized adaptive testing. Although literature on parameter recovery in unidimensional IRT abounds, less is known about parameter recovery in multidimensional IRT (MIRT), notably when tests exhibit complex structures or when latent traits are nonnormal. The current simulation study focuses on investigation of the effects of complex item structures and the shape of examinees' latent trait distributions on item parameter recovery in compensatory MIRT models for dichotomous items. Outcome variables included bias and root mean square error. Results indicated that when latent traits were skewed, item parameter recovery was generally adversely impacted. In addition, the presence of complexity contributed to decreases in the precision of parameter recovery, particularly for discrimination parameters along one dimension when at least one latent trait was generated as skewed.

Use of neuromuscular blockade with rocuronium bromide for intubation in cats.

OBJECTIVE: To determine whether neuromuscular blockade with rocuronium bromide (RB) would improve endotracheal intubation (EI) conditions in comparison with topical lidocaine hydrochloride (LH). STUDY DESIGN: Randomized prospective study. ANIMALS: Forty seven healthy cats of unspecified breed, aged 17 ± 11 months and weighing 2.8 ± 0.8 kg, undergoing elective procedures. METHODS: Anesthesia was induced with xylazine (XZ) (1.1 mg kg(-1) IM) and tiletamine-zolazepam (XTZ) (7 mg kg(-1) IM) and EI was attempted. Cats which could not be intubated at the first attempt (n = 34), were randomly medicated with either 0.1 mL LH 10% spray on the laryngeal mucosa (n = 17) or 0.6 mg kg(-1) intravenous RB (n = 17). Sixty seconds later, a second attempt at EI was performed. The effect of both drugs was assessed using a previously published scale (Sandor Agoston). EI conditions associated with laryngoscopy, vocal cord position and movement, cough, patient movement, time and attempts needed in order to perform EI were recorded. Heart rate and end-expired CO2 concentration were monitored. RESULTS: Groups were comparable in age, weight, gender and hematological parameters. Clinically acceptable EI conditions were not significantly different between RB and LH assisted groups (p = 0.31). However, there was a significant difference in cough, vocal cord movement and position between the RB and the LH groups. The group intubated at the first attempt and receiving neither RB nor LH coughed persistently (11/13). The cats receiving RB had to be ventilated for 10-28 minutes. CONCLUSIONS AND CLINICAL RELEVANCE: The present study shows that, when used in cats anesthetized with XTZ, RB paralyzes the internal laryngeal muscles keeping the vocal cords in an intermediate position (paramedial) 60 seconds after being administered. RB is an effective alternative to LH to overcome the airway protective reflexes when performing EI but requires ventilatory support until the paralysis wears off.

Surveillance for Mycobacterium bovis transmission from domestic cattle to wild ruminants in a Mexican wildlife-livestock interface area.

OBJECTIVE: To assess the prevalence of Mycobacterium bovis infection in cattle and wild ruminants (WRs) in a wildlife-livestock interface area (WLIA) of the Mexican highland plateau. ANIMALS: 24,400 cattle from 793 herds (including 17,351 commercially slaughtered cattle) and 142 WRs (110 white-tailed deer [Odocoileus virginianus], 20 red deer [Cervus elaphus], and 12 North American elk [Cervus canadensis]) harvested via controlled hunting. PROCEDURES: Cattle were serially tested for M bovis infection via caudal fold tuberculin and comparative cervical tuberculin tests during field surveillance. Carcasses of cattle and WRs were inspected for gross lesions; samples suggestive of tuberculosis were analyzed via histologic evaluation and mycobacterial culture (HMC). A PCR assay to detect Mycobacterium tuberculosis complex organisms was performed to confirm positive results of HMC. RESULTS: WRs had inflammatory lesions in lungs and lymph nodes, although HMC results did not indicate M bovis infection. Eight cattle had positive results for both tuberculin tests, and 31 had positive results for HMC of grossly detected lesions; all were from 7 herds, and ≥ 1 cow in each herd had positive PCR assay results. These 7 herds were depopulated; adjacent herds and herds related via commerce were quarantined. Calculated true prevalence of M bovis infection was 0.86% (95% confidence interval, 0.24% to 1.49%) in cattle; M bovis was not detected in any WRs. CONCLUSIONS AND CLINICAL RELEVANCE: M bovis infection was present in cattle. Although transmission to WRs in this WLIA was not detected, diagnosis and prevention activities should be implemented and consolidated to prevent potential M bovis transmission between cattle and WRs.