_____ index is the useful tool for identifying proportion of respondents giving correct response to an item.

Correct option is D

The item difficulty index (also called facility index) is a statistical measure that indicates the proportion or percentage of respondents who answered a test item correctly. It is calculated by dividing the number of correct responses by the total number of responses. This index helps test developers understand how challenging each question is for the target population.

Information Booster:
• Item difficulty index ranges from 0.0 (no one got it right) to 1.0 (everyone got it right)
• An ideal difficulty level is typically around 0.5 to 0.7 for most educational assessments
• Very easy items (difficulty > 0.9) may not effectively discriminate between high and low performers
• Very difficult items (difficulty < 0.1) may be too challenging and need revision
• The index helps in creating balanced tests with appropriate difficulty distribution
• It's essential for test validation and item analysis in psychometrics

Additional Knowledge:
• Option 1: Item reliability refers to the consistency of an item's measurement, not the proportion of correct responses
• Option 2: Item validity concerns whether an item measures what it's supposed to measure, not response proportions
• Option 3: Item discrimination measures how well an item differentiates between high and low performers, not the proportion of correct responses