The effects of changing the deletion direction and deletion ratio on the validity and reliability of the C-test

 This study looks at the effects of changing the deletion direction and ratio on the validity and reliability of the C-test. For this purpose, a cluster sampling procedure was used to select 324 English students with different levels of proficiency. The subjects were then randomly assigned to three experimental groups. Each group took a TOEFL test and a C-test version. The three C-test versions were all based on the same texts. Immediately after completing the C-test, subjects received a ten-item questionnaire about issues such as face validity, suitability, and possible functions of the C-test. The findings indicated that changing the deletion ratio from 2 to 3 can result in an easier C-test with a higher discrimination power and a better criterion-related validity. On the other hand, changing the deletion direction (from right to left) can result in a more difficult C-test with a lower discrimination power and a worse concurrent validity –a C-test which might be a completely different test that measures a different construct. However, the changes to the deletion technique probably do not result in any changes to the reliability.

The effects of changing the deletion direction and deletion ratio on the validity and reliability of the C-test Keywords:

C-test , deletion direction , deletion ratio , Validity , Reliability