Another popular topic of studies with vocabulary tests is the relationship between distractors and test difficulty.
This study focuses on the change of test difficulty by different types of distractors.
The item (or Rasch) map and the person and item separation indices indicate a good fit between the test difficulty and elementary student ability.
Furthermore, although distractors, which represent the unique characteristics of MC tests, are known to influence test difficulty, studies have focused only on the semantic relationship between target words and distractors in vocabulary tests.
Differences in test difficulty, which may possibly be larger than the results of this study indicate, are easily avoidable through the application of IRT to trailing of potential test items, item banking, and the compilation of new tests whose difficulty curves closely coincide with an established standard.
Using the same test across a wide range of grades raises a problem; depending on test difficulty, the results can be affected by severe ceiling effects in higher grades or extreme floor effects in lower grades.
A key finding by Gilks and Trejos was that large fluctuations in the pass rates were likely to be the result of variations in test difficulty rather than differences in the ability of the test takers.
Moreover, we studied publication bias and four moderators: test difficulty, presence of boys, gender equality within countries, and the type of control group that was used in the studies.
In situations where learners take a test multiple times, as is common for high-stakes tests such as IELTS and TOEFL, it could be assumed that learners modify their strategies on the basis of their experience of and initial performance on the test (i.e., test difficulty).
Participants' characteristics and values, including their knowledge and understanding of the test, resources to meet the test demands and their acceptance of these demands, as well as their perceptions of test importance and test difficulty, may all mediate washback (Green 2007).
