Applications of Hadamard transform-gas chromatography/mass spectrometry to the detection of acetone in healthy human and diabetes mellitus patient breath.

The Hadamard transform-gas chromatography/mass spectrometry (HT-GC/MS) technique was successfully employed to detect acetone, a biomarker for diabetes mellitus (DM) prediction, in human breath. Samples of exhaled breath were collected from four DM patients (one type-I and three type-II) and eight volunteers (nondiabetic healthy subjects), respectively. The gas samples, without any pretreatment, were simultaneously injected into a GC column through a Hadamard-injector based on Hadamard codes. Under optimized conditions, when cyclic S-matrix orders of 255, 1023 and 2047 were used, the S/N ratios of the acetone signals were substantially improved by 8.0-, 16.0- and 22.6-fold, respectively; these improvements are in good agreement with theoretically calculated values. We found that the breath acetone concentration levels in the four DM patients and the eight volunteers ranged from 1 to 10 ppmv and 0.1 to 1 ppmv, respectively.

NBDE Part II practice analyses: an overview.

The Standards for Educational and Psychological Testing emphasize the importance of documenting and describing the procedures followed in developing valid test content. As a result, the Joint Commission on National Dental Examinations, the testing agency responsible for administering the National Board Dental Examination Part I and Part II, routinely communicates information about the validity of Part II to dental schools and other communities of interest. Since 2000, the content of Part II has been validated through the use of three practice analyses. This article provides an overview of these practice analyses, including procedures and findings. In general, the findings confirm that the content of Part II is valid in determining the qualifications of individuals seeking dental licensure.

Assessing context effects on test validity of the National Board Dental Examination Part I.

In support of actions taken by the Joint Commission on National Dental Examinations, two changes--the inclusion of testlet items and the random presentation of items in an interdisciplinary format--were made to enhance the test validity of the National Board Dental Examination Part I in 2007. As a result, the examination was changed from a conjunctive to a comprehensive format. It was assumed that validity would be enhanced with regard to the examination's internal structure, while not disturbing item performance and examinee score. This study of the results found that 1) three underlying variables were extracted from the conjunctive Part I but only two underlying variables from the comprehensive Part I and 2) the differences in item performance and examinee score were generally small in effect size across formats. Factor analyses revealed that Part I was more discipline-sensitive for the conjunctive format but more item format-sensitive for the comprehensive format. The revision of Part I changed the nature of the examination from a discipline-based format to a more clinically relevant, interdisciplinary format, a favorable outcome anticipated by the Joint Commission. The results of this study provide evidence supporting the validity of the revised Part I examination for its intended purpose in the licensure process.

Using Rasch analysis to construct a Clinical Problem-Solving Inventory in the dental clinic: a case study.

A 28-item inventory was developed to measure the clinical problem-solving abilities of 3rd and 4th year dental students. The judgments of 57 expert raters (dental-school faculty) from four dental schools used the inventory to evaluate 183 dental students on a 5-point rating scale. The Rasch measurement model was employed to examine the psychometric properties and construct validity of this inventory. In this study, fit statistics identified the "noise" in the data and residual analysis assisted in extracting a meaningful structure. The study results indicate that the Rasch measurement model appeared to be a useful method for use in producing a unidimensional instrument. All five rating categories were used in a coherent manner, and four discernable levels of clinical problem-solving ability were identified. After removal of four repetitious items, a version of the Clinical Problem-Solving Inventory was finalized that could serve as a criterion measure for validating the use of a critical thinking test on the Dental Admission Test.

Examining item difficulty and response time on perceptual ability test items.

This study examined item calibration stability in relation to response time and the levels of item difficulty between different response time groups on a sample of 389 examinees responding to six different subtest items of the Perceptual Ability Test (PAT). The results indicated that no Differential Item Functioning (DIF) was found and a significant correlation coefficient of item difficulty was formed between slow and fast responders. Three distinct levels of difficulty emerged among the six subtests across groups. Slow responders spent significantly more time than fast responders on the four most difficult subtests. A positive significant relationship was found between item difficulty and response time across groups on the overall perceptual ability test items. Overall, this study found that: 1) the same underlying construct is being measured across groups, 2) the PAT scores were equally useful across groups, 3) different sources of item difficulty may exist among the six subtests, and 4) more difficult test items may require more time to answer.