Difficulty Index ✅

The video introduces the topic of difficulty index, emphasizing its importance in creating developmentally appropriate test questions. The goal is to avoid extremely difficult or basic questions, aiming for a moderate level. Questions that are too difficult or too easy are initially discarded but then often revised to become moderate.

Using an example of a difficulty index of 0.20, the video explains that this means only 20% of students answered correctly, while 80% answered incorrectly. This indicates a very difficult question, which is considered inappropriate and should be discarded to maintain developmental appropriateness.

The video then illustrates a difficulty index of 0.90, signifying that 90% of students answered correctly and only 10% were wrong. This shows a very easy question. Similar to very difficult questions, these are also deemed inappropriate and should be discarded.

A difficulty index of 0.50 is presented as the ideal, meaning 50% of students answered correctly and 50% incorrectly. This represents a moderate question that is developmentally appropriate and should be retained without changes.

The video summarizes the actions for different difficulty index ranges: 0-0.20 (very difficult) and 0.81-1 (very easy) should be discarded. Questions in the ranges 0.21-0.40 (difficult) and 0.61-0.80 (easy) should be revised to bring them closer to moderate, becoming either easier or more challenging, respectively. Questions within the 0.41-0.60 range (moderate) are retained.