Although cognitive diagnostic models (CDMs) can be useful in the analysis and interpretation of existing tests, little has been developed to specify how one might construct a good test using aspects of the CDMs. This article discusses the derivation of a general CDM index based on Kullback-Leibler information that will serve as a measure of how informative an item is for the classification of examinees. The effectiveness of the index is examined for items calibrated using the deterministic input noisy “and” gate model (DINA) and the reparameterized unified model (RUM) by implementing a simple heuristic to construct a test from an item bank. When compared to randomly constructed tests from the same item bank, the heuristic shows significant improvement in classification rates.

According to the weak local independence approach to defining dimensionality, the fundamental quantities for determining a test's dimensional structure are the covariances of item-pair responses conditioned on examinee trait level. This paper describes three dimensionality assessment procedures-HCA/CCPROX, DIMTEST, and DETECT—that use estimates of these conditional covariances. All three procedures are nonparametric ; that is, they do not depend on the functional form of the item response functions. These procedures are applied to a dimensionality study of the LSAT, which illustrates the capacity of the approaches to assess the lack of unidimensionality, identify groups of items manifesting approximate simple structure, determine the number of dominant dimensions, and measure the amount of multidimensionality. Index terms: approximate simple structure, conditional covariance, DETECT , dimensionality, DIMTEST, HCA/CCPROX, hierarchical cluster analysis, IRT, LSAT, local independence, multidimensionality, simple structure.

A comprehensive approach to assessing physician job satisfaction yielded 10 facets, some of which had not been previously identified, and generated a matching pool of items for subsequent use in field tests.

Physician job satisfaction is a complex phenomenon that can be measured using the PWS.

Preclinical studies have shown that the inhibition of ornithine decarboxylase (ODC) by α-difluoromethylornithine (DFMO) and resultant decreases in tissue concentrations of polyamines (putrescine and spermidine) prevents neoplastic developments in many tissue types. Clinical studies of oral DFMO at 500 mg/m 2 /day revealed it to be safe and tolerable and resulted in significant inhibition of phorbol ester-induced skin ODC activity. Two hundred and ninety-one participants (mean age, 61 years; 60% male) with a history of prior nonmelanoma skin cancer (NMSC; mean, 4.5 skin cancers) were randomized to oral DFMO (500 mg/m 2 /day) or placebo for 4 to 5 years. There was a trend toward a history of more prior skin cancers in subjects randomized to placebo, but all other characteristics including sunscreen and nonsteroidal antiinflammatory drug use were evenly distributed. Evaluation of 1,200 person-years of follow-up revealed a new NMSC rate of 0.5 events/person/year. The primary end point, new NMSCs, was not significantly different between subjects taking DFMO and placebo (260 versus 363 cancers, P = 0.069, two-sample t test). Evaluation of basal cell (BCC) and squamous cell cancers separately revealed very little difference in squamous cell cancer between treatment groups but a significant difference in new BCC (DFMO, 163 cancers; placebo, 243 cancers; expressed as event rate of 0.28 BCC/person/year versus 0.40 BCC/person/ year, P = 0.03). Compliance with DFMO was >90% and it seemed to be well tolerated with evidence of mild ototoxicity as measured by serial audiometric examination when compared with placebo subjects. The analysis of normal skin biopsies revealed a significant (P < 0.05) decrease in 12-0-tetradecanoylphorbol-13-acetate-induced ODC activity (month 24, 36, and 48) and putrescine concentration (month 24 and 36 only) in DFMO subjects. Subjects with a history of skin cancer taking daily DFMO had an insignificant reduction (P = 0.069) in new NMSC that was predominantly due to a marked reduction in new BCC. Based on these data, the potential of DFMO, alone or in combination, to prevent skin cancers should be explored further. Cancer Prev Res; 3(1); 35-47. ©2010 AACR.

item characteristic curve, kernel smoothing, large sample theory, nonparametric regression,

Cognitive diagnostic models (CDMs) model the probability of correctly answering an item as a function of an examinee's attribute mastery pattern. Because estimation of the mastery pattern involves more than a continuous measure of ability, reliability concepts introduced by classical test theory and item response theory do not apply. The cognitive diagnostic index (CDI) measures an item's overall discrimination power, which indicates an item's usefulness in examinee attribute pattern estimation. Because of its relationship with correct classification rates, the CDI was shown to be instrumental in cognitively diagnostic test assembly. This article generalizes the CDI to attribute-level discrimination indices for an item. Two different attribute-level discrimination indices are defined; their relationship with correct classification rates is explored using Monte Carlo simulations. There are strong relationships between the defined attribute indices and correct classification rates. Thus, one important potential application of these indices is test assembly from a CDM-calibrated item bank.

Variegated or milk thistle (Silybum marianum) was grown in various field trials in New Zealand, and the seed analysed for silymarin content and composition. The trials were a time of sowing trial with a New Zealand line and a German cultivar, an analysis of plant parts of the German cultivar, a time of seed harvest trial with the German and a Polish cultivar, and a comparison of seed of 25 ecotypes of the New Zealand line from a range of sites, either as collected, or after growing together on one site. Sowing date had a small effect on silymarin concentration, but not on silymarin composition. There were large differences between cultivars in seed silymarin content and composition. The New Zealand line had 18g/kg of silymarin, whereas the H06018; Online publication date