A developer is interested in deriving an index of the difficulty of the average item for his math test. As his consultant on test development, you advise him that this index could be obtained by:.

By averaging the item-difficulty indices for all test items and then dividing by the total number of items on the test.

Explanation:

An item analysis deals with  examining of the the response of student of individual test questions. examiners usually have different ways in which they determine the validity of their assessment. the method use to achieve this item analysis is by item-difficulty index and item discrimination index.

determining the validity of student's individual question item is very important as it helps the examiner to know the quality of the whole item and  of the test.

The Item-Difficulty Index in the educational field is useful in testing for validity of test question. it is known as the amount or percentage of students who answer the test questions correctly. it is often called P-value. Item-Difficulty has the range of 0-100. the formula is achieve by the number of students who answer a question correctly  divided by the total number of students in the class who answered the question(s).

i think it is the third one.

answer; society;