There are three common types of item analysis which provide teachers with three different types of information. By using the internal criterion of total test score, item analyses reflect internal consistency of items rather than validity. There are actually several ways to compute an item discrimination, but. When an alternative is worth other than a single point, or when there is more than one correct alternative per question, the item difficulty is the average score on that item divided by the highest number of points for any one alternative.
Item analysis is an essential tool used in the evaluation of the quality of mcq examinations. Two principal measures used in item analysis are item difficulty and item discrimination. Item difficulty index item difficulty index the proportion of test takers who answer an item correctly for maximizing validity and reliability, the optimal item difficulty level is 0. Dec 11, 2018 performing item analysis is one way that test makers can assess the validity of individual items on their tests. The p proportion value statistics ranges from 0 to 1. The basic procedure was to select items of difficulty a 910 and, by revising the distracters, make such items easier. Item discrimination can be calculated by ranking the students according to total score and then selecting the top 27 percent and the lowest 27 percent in terms of total score. Item analysis is essential in improving items which will be used again in later tests. It investigates the performance of items considered individually either in relation to some external criterion or in relation to the. For example, if 100 participants answered the item, and 72 of them answered the item correctly, then the p value is 0. Role of item difficulty difficulty of a test item is a function of both the item and the taker thus, indexes of relative difficulty are needed for different groups of test takers allows determination of how appropriate test items are, as well as where to place the item in a test measuring item difficulty first, use objective. Determining item difficulty and the item discrimination index can show the value of test questions, such as how well each question shows test takers mastery of the material.
Pdf relationship between item difficulty and discrimination. Higher values denote easier items more people answered the item correctly, and lower values denote harder items fewer people answered the item correctly. Item analysis data are not synonymous with item validity. The item discrimination index d, however, measures the difference between the percentage of students in the upper group p u, i. Item analysis uses statistics and expert judgment to evaluate tests based on the quality of individual items, item sets, and entire sets of items, as well as the relationship of each item to other items. To compute the item difficulty, divide the number of people answering the item correctly by the total number of people answering item. Cara menghitung uji reliabilitas, daya beda dan tingkat kesukaran menggunakan microsoft excel duration. Part iii of the item analysis output, an item quintile table, can aid in the interpretation of part iv of the output.
Relationships between the item difficulty and discrimination. Improvement in the test through item analysis can save a lot of time and energy on the part of teachers and test developer. Compute a difficulty index for each item for instructed and uninstructed groups. In either case, the item may add to the unreliability of the test because it does not aid in differentiating between those students who know the material and those who do not. Difficulty index pvalue, also called ease index, describes the percentage of students who correctly answered the item. Actually, the p stands for the proportion of participants who got the item correct. It is a scientific way of improving the quality of tests and test items in an item bank. The mcq items were analyzed for difficulty index, discriminating index, reliability, blooms cognitive levels, item writing flaws iwfs and mcqs nonfunctioning distractors nfds based test.
Analyzing item difficulty and discrimination item difficulty. Another step which leads the calculation of item difficulty and item discrimination of a test is item selection based. Identify poor items such as those answered incorrectly by many examinees. If 90% of a standard group pass an item, it is easy. Item analysis with spss software linkedin slideshare. The discrimination index of an item is the ability to distinguish high and low scoring learners. For the difficulty index, 27 testtakers answers the item correctly. For example an item answered correctly by 70% examinees has a difficulty index of 0. The quality of the multiplechoice questions mcqs used in educational measurement. Using reliability and item analysis to evaluate a teacher. Each exam paper consisted of 6080 fiveoption items. Review the item difficulty p, discrimination rit, and. It is more important for an item to be discriminable, than it is to be difficult.
The study involves ten 40 item multiplechoice mathematics tests. A value of 1 means that the item discriminates perfectly except in the wrong direction. In order to increase efficient use of both the examiners and the examinees time, the item difficulty index values can be used to order the administration items so that a discontinue rule can be invoked to reduce the administration of more difficult items to individuals who would be unlikely to pass them. Aaron dewald explains how a simple calculation can illustrate which of your exam questions are great, which are too difficult, and. Item6 has a high difficulty index, meaning that it is very easy. For polytomous items items with more than one point, classical item difficulty is the mean response value. Items having pvalues below 30% and above 70% are considered difficult and easy items respectively. Relationship between item difficulty and discrimination.
Of 30 items, 11 items were of higher difficulty level dif i 60%. Item difficulty is important because it reveals whether an item is too easy or too hard. Mean difficulty index p and discrimination index d for each mcq paper analysed for. Difficulty index is defined as the percentage of those candidates recording either a true or false response for a particular branch in a multiple truefalse response mcq who gave the correct response. The closer the difficulty of an item approaches to zero, the more difficult that item is.
The study focused on item and test quality and explored the relationship between difficulty index pvalue and discrimination index. Assessing item difficulty and discrimination indices of. See sample test frequency distribution download pdf item difficulty and discrimination. This measure asks teachers to calculate the proportion of students who answered the test item accurately.
Recommended difficulty index for various test items. An item answered correctly by 35% of the examinees has an item difficulty level of. This measure asks teachers to calculate the proportion of students who answered the test item. The proportion of students answering an item correctly indicates the difficulty level of the item. In classical test theory, a common item statistic is the item s difficulty index, or p value. Item analysis basic concepts real statistics using excel. This value would tell us that the weaker students performed better on an item than the better. Item difficulty index dif i and discrimination index di.
The relationship between item difficulty index and discrimination index values of the mcq papers n 250 test items for parts a, b and c examinations, administered to 155 year ii medical students in the university of malaya, session 20012002. Item analysis is a process of examining classwide performance on individual test items. Optimally, an item will encourage a widespread distribution of scores if its difficulty index is approximately 0. Pdf difficulty index, discrimination index and distractor. Item analysis report item difficulty index questionmark.
Part iv compares the item responses versus the total score distribution for each item. Canvas quiz item analysis difficulty index alpha score for the whole exam point biserial of the correct answer reliability index point biserial of the first incorrect answer or distractor followed by the second, etc. The division among hard, medium, and easy levels of difficulty and good, fair, and poor levels of discrimination are somewhat arbitrary. Interpreting the item analysis report stony brook university. Jun 23, 2016 cara menghitung uji reliabilitas, daya beda dan tingkat kesukaran menggunakan microsoft excel duration. When multiplied by 100, p value converts to a percentage, which is the percentage of students who got the item correct. The average difficulty index of the 4 basic skills test items was 0. Difficulty index, discrimination index, sensitivity and. There is a variety of reasons an item may have low discriminating power.
In this cross sectional study 65 items responded by 120 students of first year m. Item difficulty item discrimination university assessment and testing item difficulty item difficulty is the proportion of examinees who got an item correct. Item difficulty, discrimination index and distractor efficiency juliana linnette dsar, maria liza visbal. This item should be carefully analyzed, and probably deleted or changed. Item discrimination index the item discrimination index is a measure of how well an item is able to distinguish between examinees who are knowledgeable and those who are not, or between masters and nonmasters. Evaluation of item difficulty for item analysis item difficulty index p item evaluation above 0. When an alternative is worth other than a single point, or when there is more than one correct alternative per question, the item. Typically, in analysis of a test, two values are computed, a difficulty level and a discrimination index. The dependence of the item discrimination index d on the item difficulty index p, and the relationship of d and p to the phi coefficient. Up and lp indicate the numbers of test takers in the upper and lower groups who pass the item, and u is the total numbers of test takers in the upper group. Given many psychometricians notoriously poor spelling, might this be due to thinking that difficulty starts with p. The optimal level for an acceptable p value depends on the number of options per item. For items with one correct alternative worth a single point, the item difficulty is simply the percentage of students who answer an item correctly.
Analysis of the difficulty and discrimination indices of. To investigate the relationship of items having good difficulty and discrimination indices with their distractor efficiency to find how ideal questions can. Performing item analysis is one way that test makers can assess the validity of individual items on their tests. Item d the assessment of internal medicine patients showed the highest difficulty index 0. Item analysis can help you evaluate how well your objective items are actually working. Assessment resources iar acknowledged values of difficulty index and their evaluation as tabulated in table 1. If no one answers the item correctly, the p value would be 0. Item difficulty item difficulty is simply the percentage of students who answer an item correctly. An external criterion is required to accurately judge the validity of test items. Item analysis discrimination and difficulty index 1. The discrimination index is not always a measure of item quality. The closer this value is to 1, the better the item. The difficulty p and discrimination r indices of the items are calculated in this analysis ozcelik, 1989.
Doc item difficulty and item discrimination nhia kurniaty. Oct 01, 2015 item analysis discrimination and difficulty index 1. An item analysis is a valuable, yet relatively easy, procedure that teachers can use to answer both of these questions. To determine the difficulty level of test items, a measure called the difficulty index is used. The item difficulty index is often called the pvalue because it is a measure of proportion for example, the proportion of students who answer a particular question correctly on a test. Item analysis is a technique which evaluates the effectiveness of items in tests. Score items 0,1 for each trainee in the instructed and uninstructed groups. Generally, items of moderate difficulty are to be preferred to those which are much easier or much harder. Individual exam item analysis for each item, you will receive a report on how many students selected each response, the item difficulty, and the item discrimination. There was a wide distribution of item difficulty indices in all the mcq. An item analysis provides three kinds of important information about the quality of test items.
An item that everyone answers correctly would have a p value of 1. Item difficulty item discrimination university assessment and testing item difficulty item difficulty is the proportion of examinees who got an item correct term is a misnomer really item easiness university assessment and testing n p number of correct responses. Compute a difficulty index for each item for in structed and uninstructed groups. The formula for the item difficulty index is p cn where, c is the number of students who selected the correct answer and n is the total number of respondents. Item analysis rensselaer polytechnic institute rpi. Using the questions and results from the tests we have investigated the relationship between the degree of difficulty of each question and the corresponding discrimination index. Item discrimination tells us how good a job a question does is separating high and low performers. The 4 items of the basic skills test significantly varied in terms of difficulty index p item difficulty index item difficulty index the proportion of test takers who answer an item correctly for maximizing validity and reliability, the optimal item difficulty level is 0.
However, there was no relationship between the item difficulty index and the item. Hence, the higher this index value, the lower is the difficulty, and the greater the difficulty of an item, the lower is its index. Item discrimination is used to determine how well an item is able to discriminate between good and poor students. Item4 and item5 are typical items, where the majority of items are responding correctly. Instructional assessment resources iar acknowledged values of difficulty index and their evaluation as.
When we subtract the proportion of low scoring students who got the item right from the proportion of high. Item difficulty may be defined as the proportion of the examinees that marked the item correctly. A table of critical values of d for significance at the. Assessmentquality test constructionteacher toolsitem. It is frequently measured by calculating the proportion of individuals passing an item.
The formula for the item discrimination index is d ul u pp where. Our results indicate that as the degree of difficulty increases so does the capability of the item to discriminate. The difference is one measure of item discrimination idis. The higher the difficulty index, the easier the item is understood to be wood, 1960. Item analysis is an important procedure to determine the quality of the items. More often, it is a sign that the item has been miskeyed. Careful examination of each of these is critical, as you will use this information to determine the quality of the item. Item difficulty index dif i and discrimination index di using point biserial correlation. What exactly is item difficulty and how do you measure it. When interpreting the value of a discrimination it is important to be aware that there is a relationship between an item s difficulty index and its discrimination index. Item difficulty is a characteristic of the item and the sample that takes the test. Discriminating power of the test items or item discrimination the above two indices help in item selection for the final draft of the test. Item difficulty and discrimination teachers who create tests for classroom use often seek to know how effective their tests are item analysis provides important information about how well items function item difficulty helps us to know the degree to which students get the answer correct. In classical test theory, a common item statistic is the items difficulty index, or p value.
Pdf difficulty index, discrimination index and distractor efficiency. Difficulty index teachers produce a difficulty index for a test item by calculating the proportion of students in class who got an item correct. Understanding item analyses office of educational assessment. Varying levels of difficulty index of skillstest items. Item difficulty is an estimate of the skill level needed to pass an item. For each item, the percentage of students in the upper and lower groups answering correctly is calculated. The more students got the item right, the less difficult the item was. When formalized, the procedure is called item analysis. Item difficulty is the percentage of learners who answered an item correctly and ranges from 0. Thus, many of the items on an nrt will have difficulty indexes between. Mean for difficulty index, discrimination index and distractor efficiency were 38.
Delta is an index of item difficulty based upon the percent of all candidates trying the item who. The purpose of this study is to assess two important indices in item analysis procedure, namely 1 item difficulty p and 2 item discrimination d as well as a correlation between them. An item answered correctly by 75% of the examinees has an item difficult level of. Items with negative indices should be examined to determine whether the item was flawed or miskeyed.
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