A Comparison of the Two-Option Versus the Four-Option Multiple-Choice Item: A Case for Fewer Distractors

Multiple choice test items typically consist of the key and 3-4 distractors. However, research has supported the efficacy of using fewer alternatives. Haladyna and Downing (1993) found that it is difficult to write test items with more than one plausible distractor, resulting in items with a correct answer and one alternative, also known as the alternate choice (AC) format. We constructed two 32-item tests; one with four alternatives (MC4) and one with two (AC), using an inter-judge agreement approach to eliminate distractors. Tests were administered to 138 personnel working for a U.S. Government agency. Testing time was significantly less and scores were higher for the AC test. However, score differences disappeared when both forms were corrected for guessing. There were no significant differences in test difficulty (mean p-values). The corrected KR-20 reliabilities for both forms, after applying the Spearman-Brown formula, were AC = .816 and MC4 = .893. We discuss the results with respect to the resources spent writing and reviewing test items, and in more broadly sampling a content domain using the AC format due to reduced testing times

An Investigation of Chi-Square and Entropy Based Methods of Item-Fit Using Item level Contamination in Item Response Theory

New variants of entropy as measures of item-fit in item response theory are investigated. Monte Carlo simulation(s) examine aberrant conditions of item-level misfit to evaluate relative (compare EMRj, X2, G2, S-X2, and PV-Q1) and absolute (Type I error and empirical power) performance. EMRj has utility in discovering misfit

Wheat receptor-kinase-like protein Stb6 controls gene-for-gene resistance to fungal pathogen Zymoseptoria tritici

Deployment of fast-evolving disease-resistance genes is one of the most successful strategies used by plants to fend off pathogens. In gene-for-gene relationships, most cloned disease-resistance genes encode intracellular nucleotide-binding leucine-rich-repeat proteins (NLRs) recognizing pathogensecreted isolate-specific avirulence (Avr) effectors delivered to the host cytoplasm. This process often triggers a localized hypersensitive response, which halts further disease development. Here we report the map-based cloning of the wheat Stb6 gene and demonstrate that it encodes a conserved wallassociated receptor kinase (WAK)-like protein, which detects the presence of a matching apoplastic effector and confers pathogen resistance without a hypersensitive response. This report demonstrates gene-for-gene disease resistance controlled by this class of proteins in plants. Moreover, Stb6 is, to our knowledge, the first cloned gene specifying resistance to Zymoseptoria tritici, an important foliar fungal pathogen affecting wheat and causing economically damaging septoria tritici blotch (STB) disease