APPLYING ITEM RESPONSES THEORY FOR MEASURING STUDENT’S ABILITY IN ACADEMIC SPEAKING

Purpose of the study: Every human being is required to be skilled at communicating, skilled at expressing thoughts, ideas, and feelings. This research aims to explain student’s ability in academic speaking based on the framework of item responses theory. Methodology: This research uses a mix method research approach; qualitative and quantitative approaches are used together to answer the formulated problems. A qualitative approach is used for digging up information about the needs to develop the speaking test. The try out subjects was 25 university student taking Bahasa Indonesia subject; while 125 students were used as the measurement subject. The data were students’ responses to the speaking test which was scored by two people (rater). The reliability of the instrument was estimated by the Generalizability theory. Rasch model analysis was used to estimate the item parameter; while the Maximum Likelihood was used to estimate the students’ ability. Main Findings: The value of 𝜎 ̂(𝑜) s influenced by the similarity to the average mean score observed in academic speaking. The value of 𝜎 ̂(𝑝) and 𝜎 ̂(𝑜) suggests that the distribution of variability in person and item is the same and high. A sufficiently large value of 𝜎 ̂(𝑝i) implies the fact that the value involves all residual sources for a variance. Balance alternatives, weigh consequently and decide rationally. Applications of this study: Based on the design proposed for the Indonesian Language Proficiency assessment, other generalizability design (G-Design) used is a cross design because each student (p) becomes the object of observation of two observers (r) who both assess four aspects of observation/indicator. It is used to determine the reliability (i.e., reproducibility) of measurements under specific conditions in academic speaking. Novelty/Originality of this study: Some rater qualifications that must be met include the process of gathering and using the appropriateness of background information before assessing. Measuring the ability of students in academic speaking by applying G theory and conducting an IRT analysis approach needs.

The Balance of Salinity Variance in a Partially Stratified Estuary: Implications for Exchange Flow, Mixing, and Stratification

Salinity variance dissipation is related to exchange flow through the salinity variance balance equation, and meanwhile its magnitude is also proportional to the turbulence production and stratification inside the estuary. As river flow increases, estuarine volume-integrated salinity variance dissipation increases owing to more variance input from the open boundaries driven by exchange flow and river flow. This corresponds to the increased efficient conversion of turbulence production to salinity variance dissipation due to the intensified stratification with higher river flow. Through the spring–neap cycle, the temporal variation of salinity variance dissipation is more dependent on stratification than turbulence production, so it reaches its maximum during the transition from neap to spring tides. During most of the transition time from spring to neap tides, the advective input of salinity variance from the open boundaries is larger than dissipation, resulting in the net increase of variance, which is mainly expressed as vertical variance, that is, stratification. The intensified stratification in turn increases salinity variance dissipation. During neap tides, a large amount of enhanced salinity variance dissipation is induced by the internal shear stress near the halocline. During most of the transition time from neap to spring tides, dissipation becomes larger than the advective input, so salinity variance decreases and the stratification is destroyed.

On the Construction of VB Designs

This paper gives complete analytical study of suitability and non-availability of I-associate and II-associate designs of a given 2-class partially balanced incomplete block (2-PBIB) design in the construction of a variance balance (VB) design using the given 2-PBIB design.

Experiments on density-gradient anisotropies and scalar dissipation of turbulence in a stably stratified fluid

The anisotropic behaviour of density-gradient fluctuations in stably stratified grid turbulence and the consequences for simplified (isotropic) estimates of scalar dissipation rates χ were experimentally studied in a thermally stratified wind tunnel at moderate Reynolds numbers (Reλ ≃ 20). Strong stable stratifications were attained, with Brunt-Väisälä frequency N as high as 4 rad s−1. The correlation method was used to estimate the mean-square cross-stream and streamwise density gradients. Cross-stream gradients were measured using two cold wires. The mean-square vertical gradients were found to become larger than the streamwise gradients by as much as a factor of 2.2 for the largest dimensionless buoyancy times (Nt = 7). This corresponds to a 40% error in the scalar dissipation estimates based on ∂θ/∂x alone, and assuming the validity of the isotropic relations. Gradient spectral relations show that this buoyancy-induced anisotropy persists at all length scales. Better closure of the scalar variance balance was attained than in previously reported measurements by other researchers. This is attributed to our use of cold-wire temperature sensors having larger length-to-diameter ratio than used in the previous measurements.