Item analysis

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Item analysis

  1. 1. ITEM ANALYSIS Dr. Rajasree Lecturer in General Education K.U.C.T.E,Aryad,Alappuzha
  2. 2. ITEM ANALYSIS  Item analysis is a statistical technique which is used for selecting and rejecting the items of the test on the basis of their difficulty value and discriminating power  Item analysis is done for obtaining: Difficulty value (D.V) Discriminative power (D.P)
  3. 3. OBJECTIVES OF ITEM ANALYSIS: To select appropriate items for the final draft To obtain the information about the difficulty value(D.V) of all the items  To provide discriminatory power (D.I) to differentiate between capable and less capable examinees for the items To provide modification to be made in some of the items To prepare the final draft properly ( easy to difficult items
  4. 4. STEPS OF ITEM ANAYSIS: Arrange the scores in descending order Separate two sub groups of the test papers Take 27% of the scores out of the highest scores and 27% of the scores falling at bottom Count the number of right answer in highest group (R.H) and count the no of right answer in lowest group (R.L) Count the non-response (N.R) examinees
  5. 5. Difficulty value (D.V): “ The difficulty value of an item is defined as the proportion or percentage of the examinees who have answered the item correctly” - J.P. Guilford The formula for difficulty value (D.V ) D.V = (R.H + R.L)/ (N.H + N.L) R.H – rightly answered in highest group, R.L - rightly answered in lowest group N.H – no of examinees in highest group, N.L - no of examinees in lowest group
  6. 6. In case non-response examinees available means, The formula for difficulty value (D.V) D.V = (R.H + R.L)/ [(N.H + N.L)- N.R] R.H – rightly answered in highest group R.L - rightly answered in lowest group N.H – no of examinees in highest group N.L - no of examinees in lowest group N.R – no of non-response examinees
  7. 7. Discrimination index (D.I): “ Index of discrimination is that ability of an item on the basis of which the discrimination is made between superiors and inferiors ” – Blood and Budd (1972) Types of discrimination index (D.I):  Zero discrimination or No discrimination  Positive discrimination  Negative discrimination
  8. 8. Zero discrimination or No discrimination : Zero discrimination or No discrimination: The item of the test is answered correctly or know the answer by all the examinee’s An item is not answered correctly by any of the examinee Positive discrimination index: Positive discrimination index :An item is correctly answered by superiors and is not answered correctly by inferiors. The discriminative power range from +1 to -1. Negative discrimination index: Negative discrimination index :An item is correctly answered by inferiors and is not answered correctly by superiors.
  9. 9. The formula for discrimination index(D.I) D.I = (R.H - R.L)/ (N.H or N.L) R.H – rightly answered in highest group R.L - rightly answered in lowest group N.H – no of examinees in highest group N.L - no of examinees in lowest group
  10. 10. General guidelines for discriminating index (D.I) According to Ebel , D.I Item Evaluation ≥0.40 -Very good items  0.30 - 0.39 Reasonably good but subject to improvement  0.20 – 0.29 Marginal items , need improvement <0.19 Poor items . Rejected or revised
  11. 11. D.V Item Evaluation 0.20 – 0.30 Most difficult 0.30 - 0.40 Difficult 0.40 – 0.60 Moderate difficult 0.60 – 0.70 Easy 0.70 – 0.80 Most easy Relationship between difficulty value and discrimination power  Both (D.V & D.I) are complementary not contradictory to each other Both should be considered in selecting good items  If an item has negatively discriminate or zero discrimination, is to be rejected whatever be the difficulty value
  12. 12. THANK YOU

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