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A COMPARISON METHOD OF EQUATING CLASSIC
AND ITEM RESPONSE
THEORY (IRT):
A CASE OF IRANIAN STUDY IN THE UNIVERSITY
ENTRANCE
EXAM
Ali Moghadamzadeh , Keyvan Salehi , Ebrahim Khodaie
International Conference on Education and Educational Psychology
(ICEEPSY 2011)
Procedia - Social and Behavioral Sciences 29 ( 2011 ) 1368 – 1372
Reporter : Yu Chih Lin
Outline

Abstract

Introduction

Methodology

Results
Abstract

Introduce the concept of equating

Compare classic equating and item response theory(IRT)


Advantages

Disadvantages
Different errors of equating

Using software’s BILOG and SPSS
Abstract


In the two tests

Equated with the same scale

Accuracy of equating was estimated
This study has implications for educational measurement and
testing procedures

Adaptive testing

Test constructing
Introduction


Equating is a statistical method , called equating of test

Relate two or more tests

Base two or more tests on a same scale
Methods of equating general can be categorized

Horizontal

Vertical
Introduction

Determining that whether tests can be equated


Dependent on the possibility of establishing the equating conditions
Equating the tests four conditions

Similar ability

Equity

Population invariance

symmetry
Methodology

To answer the intended items, the subjects for this population
were considered

People were all Iranian

Taking the test in the field of Test of language

By The Iranian measurement organization (TOLIMO)
Methodology


Sample size

sampling error of 0.5 %

confidence level of 95 %
for form A


1054 participants
for form B

1241 participants
Methodology


This test is based on three

Sub-scales of vocabulary

Structure

Listening
In this test eight questions were selected as anchor questions

According grades of the forms of A and B
Results
Table 1: Deceptive statistics
Table 2: Summary of Results
Results

Classic method has a little equating between the forms of A
and B

Determining the constants, it is not needed to regard
symmetry

Generally very difficult to be established in the classic method

Showed the regression indexes were influenced

Respectively the forms of A and B were the references
Results

Results showed that in the classic method

Equating is dependent to the observed sample

IRT can resolve two limits of classic method, symmetry and
invariance

In IRT if the model be fitted with the data, parameters of
ability can be measured
Results


In the form of A

difficulty (𝑏𝐴 )

discrimination (𝑎𝐴 )
In the form of B

difficulty (𝑏𝐵 )

discrimination (𝑎𝐵 )
Results

In addition, with IRT the parameter of ability (TETA)

Showed that the parameter of discrimination and difficulty

In different mentioned states were not significantly different