An EM-Based Method for Q-Matrix Validation

Determining the number of attributes in the GDINA model

Exploratory cognitive diagnosis models have been widely used in psychology, education and other fields. This paper focuses on determining the number of attributes in a widely used cognitive diagnosis model, the GDINA model. Under some conditions of cognitive diagnosis models, we prove that there exists a special structure for the covariance matrix of observed data. Due to the special structure of the covariance matrix, an estimator based on eigen-decomposition is proposed for the number of attributes for the GDINA model. The performance of the proposed estimator is verified by simulation studies. Finally, the proposed estimator is applied to two real data sets Examination for the Certificate of Proficiency in English (ECPE) and Big Five Personality (BFP).

Using machine learning to improve Q-matrix validation

The Q-matrix, which specifies the relationship between items and attributes, is a crucial component of cognitive diagnostic models (CDMs). A precisely specified Q-matrix allows for valid cognitive diagnostic assessments. In practice, a Q-matrix is usually developed by domain experts, and noted as being subjective and potentially containing misspecifications which can decrease the classification accuracy of examinees. To overcome this, some promising validation methods have been proposed, such as the general discrimination index (GDI) method and the Hull method. In this article, we propose four new methods for Q-matrix validation based on random forest and feed-forward neural network techniques. Proportion of variance accounted for (PVAF) and coefficient of determination (i.e., the McFadden pseudo-R2) are used as input features for developing the machine learning models. Two simulation studies are carried out to examine the feasibility of the proposed methods. Finally, a sub-dataset of the PISA 2000 reading assessment is analyzed as illustration.

A multiple logistic regression-based (MLR-B) Q-matrix validation method for cognitive diagnosis models:A confirmatory approach

Q-matrix is an essential component specifying the relationship between attributes and items, which plays a key role in cognitive diagnosis assessment. The Q-matrix is usually developed by domain experts and its specifications tend to be subjective and might have misspecifications. Many existing pieces of research concentrate on the validation of Q-matrix; however, few of them can be applied to saturated cognitive diagnosis models. This paper proposes a general and effective Q-matrix validation method by employing multiple logistic regression model. Simulation studies are carried out to investigate the performance of the proposed method and compare it with four existing methods. Simulation results indicate the proposed method outperforms the existing methods in terms of validation accuracy. In addition, a set of real data is used as an example to illustrate its application. Finally, we discuss the limitations of the current study and the directions of future studies.

Data-driven Q-matrix validation using a residual-based statistic in cognitive diagnostic assessment

In a cognitive diagnostic assessment (CDA), attributes refer to fine-grained knowledge points or skills. The Q-matrix is a central component of CDA, which specifies the relationship between items and attributes. Oftentimes, attributes and Q-matrix are defined by subject-matter experts, and assumed to be appropriate without any misspecifications. However, this assumption does not always hold in real applications. To address this concern, this paper proposes a residual-based statistic for validating the Q-matrix. Its performance is evaluated in a simulation study and compared against that of an existing method proposed in Liu, Xu and Ying (2012, Applied Psychological Measurement, 36, 548). Simulation results indicate that the proposed method leads to a higher recovery rate of the Q-matrix and is computationally more efficient. The advantage in computational efficiency is particularly pronounced when the number of attributes measured by the test reaches five or more. Results also suggest that the two methods have different tendencies in estimating the attribute vector for each item. In cases where the methods fail to recover the correct Q-matrix, the method in Liu et al. (2012, Applied Psychological Measurement, 36, 548) tends to overestimate the number of attributes measured by the items, whereas our method does not show that bias.

A Semi-supervised Learning Method for Q-Matrix Specification Under the DINA and DINO Model With Independent Structure

Cognitive diagnosis assessment (CDA) can be regarded as a kind of formative assessments because it is intended to promote assessment for learning and modify instruction and learning in classrooms by providing the formative diagnostic information about students' cognitive strengths and weaknesses. CDA has two phases, like a statistical pattern recognition. The first phase is feature generation, followed by classification stage. A Q-matrix, which describes the relationship between items and latent skills, corresponds to the feature generation phase in statistical pattern recognition. Feature generation is of paramount importance in any pattern recognition task. In practice, the Q-matrix is difficult to specify correctly in cognitive diagnosis and misspecification of the Q-matrix can seriously affect the accuracy of the classification of examinees. Based on the fact that any columns of a reduced Q-matrix can be expressed by the columns of a reachability R matrix under the logical OR operation, a semi-supervised learning approach and an optimal design for examinee sampling were proposed for Q-matrix specification under the conjunctive and disjunctive model with independent structure. This method only required subject matter experts specifying a R matrix corresponding to a small part of test items for the independent structure in which the R matrix is an identity matrix. Simulation and real data analysis showed that the new method with the optimal design is promising in terms of correct recovery rates of q-entries.

Improving Robustness in Q-Matrix Validation Using an Iterative and Dynamic Procedure

In the context of cognitive diagnosis models (CDMs), a Q-matrix reflects the correspondence between attributes and items. The Q-matrix construction process is typically subjective in nature, which may lead to misspecifications. All this can negatively affect the attribute classification accuracy. In response, several methods of empirical Q-matrix validation have been developed. The general discrimination index (GDI) method has some relevant advantages such as the possibility of being applied to several CDMs. However, the estimation of the GDI relies on the estimation of the latent group sizes and success probabilities, which is made with the original (possibly misspecified) Q-matrix. This can be a problem, especially in those situations in which there is a great uncertainty about the Q-matrix specification. To address this, the present study investigates the iterative application of the GDI method, where only one item is modified at each step of the iterative procedure, and the required cutoff is updated considering the new parameter estimates. A simulation study was conducted to test the performance of the new procedure. Results showed that the performance of the GDI method improved when the application was iterative at the item level and an appropriate cutoff point was used. This was most notable when the original Q-matrix misspecification rate was high, where the proposed procedure performed better 96.5% of the times. The results are illustrated using Tatsuoka's fraction-subtraction data set.

A Constrained Metropolis-Hastings Robbins-Monro Algorithm for Q Matrix Estimation in DINA Models

In diagnostic classification models (DCMs), the Q matrix encodes in which attributes are required for each item. The Q matrix is usually predetermined by the researcher but may in practice be misspecified which yields incorrect statistical inference. Instead of using a predetermined Q matrix, it is possible to estimate it simultaneously with the item and structural parameters of the DCM. Unfortunately, current methods are computationally intensive when there are many attributes and items. In addition, the identification constraints necessary for DCMs are not always enforced in the estimation algorithms which can lead to non-identified models being considered. We address these problems by simultaneously estimating the item, structural and Q matrix parameters of the Deterministic Input Noisy "And" gate model using a constrained Metropolis-Hastings Robbins-Monro algorithm. Simulations show that the new method is computationally efficient and can outperform previously proposed Bayesian Markov chain Monte-Carlo algorithms in terms of Q matrix recovery, and item and structural parameter estimation. We also illustrate our approach using Tatsuoka's fraction-subtraction data and Certificate of Proficiency in English data.

Q-Matrix Estimation Methods for Cognitive Diagnosis Models: Based on Partial Known Q-Matrix

Different from the item response models that postulate a single underlying proficiency, cognitive diagnostic assessments (CDAs) can provide fine-grained diagnostic information about students' knowledge state to aid classroom instructions. In CDAs, a Q-matrix that associates each item in a test with the cognitive skills is required to infer students' knowledge states. In practice, the Q-matrix is typically performed by domain experts, which is certainly affected by the subjective tendency of experts and, to a large extent, may consist of some misspecifications. In addition, if the number of items increases, the expert-based Q-matrix specification will be time-consuming and costly. To address this concern, this paper proposed several approaches based on the likelihood ratio test to estimate Q-matrix with partial known Q-matrix and the response data, which can be used with a wide class of cognitive diagnosis models (CDMs). The feasibility and effectiveness of the proposed methods were evaluated by simulated data generated under various conditions and an example to real data. Results show that new methods can estimate Q-matrix correctly and outperforms the existing method in most conditions.

An empirical Q-matrix validation method for the sequential generalized DINA model

As a core component of most cognitive diagnosis models, the Q-matrix, or item and attribute association matrix, is typically developed by domain experts, and tends to be subjective. It is critical to validate the Q-matrix empirically because a misspecified Q-matrix could result in erroneous attribute estimation. Most existing Q-matrix validation procedures are developed for dichotomous responses. However, in this paper, we propose a method to empirically detect and correct the misspecifications in the Q-matrix for graded response data based on the sequential generalized deterministic inputs, noisy 'and' gate (G-DINA) model. The proposed Q-matrix validation procedure is implemented in a stepwise manner based on the Wald test and an effect size measure. The feasibility of the proposed method is examined using simulation studies. Also, a set of data from the Trends in International Mathematics and Science Study (TIMSS) 2011 mathematics assessment is analysed for illustration.

Incorporating the Q-Matrix Into Multidimensional Item Response Theory Models

Multidimensional item response theory (MIRT) models use data from individual item responses to estimate multiple latent traits of interest, making them useful in educational and psychological measurement, among other areas. When MIRT models are applied in practice, it is not uncommon to see that some items are designed to measure all latent traits while other items may only measure one or two traits. In order to facilitate a clear expression of which items measure which traits and formulate such relationships as a math function in MIRT models, we applied the concept of the Q-matrix commonly used in diagnostic classification models to MIRT models. In this study, we introduced how to incorporate a Q-matrix into an existing MIRT model, and demonstrated benefits of the proposed hybrid model through two simulation studies and an applied study. In addition, we showed the relative ease in modeling educational and psychological data through a Bayesian approach via the NUTS algorithm.

Reconsidering Cutoff Points in the General Method of Empirical Q-Matrix Validation

Cognitive diagnosis models (CDMs) are latent class multidimensional statistical models that help classify people accurately by using a set of discrete latent variables, commonly referred to as attributes. These models require a Q-matrix that indicates the attributes involved in each item. A potential problem is that the Q-matrix construction process, typically performed by domain experts, is subjective in nature. This might lead to the existence of Q-matrix misspecifications that can lead to inaccurate classifications. For this reason, several empirical Q-matrix validation methods have been developed in the recent years. de la Torre and Chiu proposed one of the most popular methods, based on a discrimination index. However, some questions related to the usefulness of the method with empirical data remained open due the restricted number of conditions examined, and the use of a unique cutoff point (EPS) regardless of the data conditions. This article includes two simulation studies to test this validation method under a wider range of conditions, with the purpose of providing it with a higher generalization, and to empirically determine the most suitable EPS considering the data conditions. Results show a good overall performance of the method, the relevance of the different studied factors, and that using a single indiscriminate EPS is not acceptable. Specific guidelines for selecting an appropriate EPS are provided in the discussion.