Océano Pacífico
1. Análisis de captura a la edad
Meaning and Definition:
Reliability means consistency of measurement in the words of Ebel and frisbie, “The ability of a test to measure the same quantity when it is administred to an individual on two different occasions by two different teser is called reliability. The reliability indicates the degree to which measurement can be relied upon, to measure the same thing each time is used.
In simple words we can say that a good measuring instrument (test) should be reliable in reporting the results if it is done by the same group of student under the same conditions.
Reliability is also called dependability or trustworthiness reliability is the degree to which a test consistently measures whatever it
measures. The more reliable a test is, the more confidence we can have that the scores obtained from the administration of the test are essentially the same scores that would be obtained if the test where re-administered.
An unreliable test is essentially useless. For example, if an intelligence test was unreliable then a student soring an IQ of 120 today might score an IQ of 140 tomorrow and a 95 the day after tomorrow. On the other hand if the test is reliable then the IQ of a student will remain nearly the same each time the test is administered. The reliability of a test depends upon the number of questions consisted by it. A test will be more reliable if it possesses more questions. In this respect, objective type tests are more reliable because its sampling is more extensive.
We can take another expert opinion to understand the meaning of reliability. “If a clinical thermo meter on three successive determinations, for example yielded reading of 97o, 103o and 99.6ofor the same patient, it would not be considered very reliable.
Reliability, of course is a necessary but not a sufficient condition for using a test. A highly reliable test may be totally invalid or may not measure anything that is psychologically of educationally significant.
The reliability of a single of a single test score is expressed quantitatively in terms of the instruments standard error of measurement.
If the standard error of measurement, for example, is 2.5, we can say that there are approximately two chances in three (more precisely 68 in 100) that the true score falls between 72.5 and 77.5 when the obtained score is 75. By definition, an unreliable test cannot possible be valid. The necessary degree of reliability however depends on the use that is made of test scores.”
Methods of Determining Reliability:
For determining reliability, it is necessary that the test should be valid and it should measure what it is designed to measure. It should be administered to an appropriate person or group of parsons for whom the test has been developed. Reliability is a statistical measure and therefore
it can be computed by using different statistical methods. Which have been stated in detail on next page.
1. Test-retest method:
When the reliability of the results are two measured, then at that very situation the test retest method is used in this method the tests are subjected to the group of students at different perrods of time. The scores obtained from first and second time can be correlated in order to check the stability and persistency of test.
In test re-test reliability the time factor counts a lot in very close retesting the results are approximately the same, yielding high correlation. But when the retest is administered after an year or two, as the result of changes in the characteristics of students, there are expected to be large variation in the outcome and therefore stability will be low.\
Limitation:
i. The co-efficient of reliability established through test-retest method is erroneous.
ii. The reliability determined through test-retest method has memory of carry over effect.
iii. The test retest method is not an objective method ascertaining reliability of the test.
2. Equivalent forms method:
The second method of ascertaining reliability is alternate form method or method of equivalence. Through this method one has to use two alternate or equivalent tests in order to establish the reliability. This method is used to see the reliability of test for measuring certain content area. It is applied to standardized tests only as they have two or more forms of the same test available.
Equivalent forms are used in the same group and in close succession. The result of both the tests are correlated. The correlation shows the degree to which both tests are measurining the same content area. Sometimes the equivalent forms are used
with time interval. Results obtained by this method provide both stability and reliability of test. This method is generally considered to be the best method.
Limitation:
i. Finding the reliability through this method is cumbersome because it is difficult to judge the quality of a test which is equivalent in each and every respect.
ii. This process is more time consuming and also it is not free from carry over effect.
iii. More over establishment of reliability through this method is not feasible for each and every type of test.
3. Split half method:
As the name indicates in Split-Half- method the approach is to split the test into two reasonable equivalent halves. Such independent sub-test are then used as a source of the two independent scores needed for reliability estimation.
In this method a test is administered to a group of students.
Before scoring, the test is split into two equal halves. Generally odds and evens are separated. By marking each part separately each student gets two different scores which are correlated. The correlation gives a measure of internal consistency, of the test.
Reliability of the test is estimated by applying spearman Brown formula:
2 x Reliabi lity on 1 2 test 1+Reliability on 1
2 test
Like equivalent forms method the split-half method helps in determining the reliability of test items are representative sample of the content.
Limitation:
i. The general criticism of split-half method is concerned with splitting on the test. As there is no rule, one may go for applying this own conscience in splitting the test into two halves. The way of splitting varies from person to person which affects the reliability coefficient.
ii. The second criticism is concerned with the items difficulty.
Generally the items of a test are arranged in ordered of difficulty but this fact is not true for each and every type of test. Say for example, without knowing the difficulty level of items if one goes for splitting all the difficulty items in one half and the simple item in another half, it will affect the reliability coefficient adversely.
4. Kuder Richardson method:
Richardson developed several formulas for measuring internal consistency of a test. Kudder Richard son formula zo and z1 and generally applied. But due to simplicity of the operation formula z1 is always preffered.
Reliability (K R Z1) =
K
K −1 [ 1− M (K −M) K S
2]
K= the number of items in the test.
M= mean of the test scores;
S= standard deviation of the test scores.
Summary: The following methods are used for determining reliability of a test.
A Test – Retest method i. Immediate (without interval) B Equivalent form method ii. With time interval
C Split half method iii. Immediate D Kuder – Richardson formula iv. With interval 5. Parallel form Reliability:
When the different sets or different parts of a test (suppose questionnaire a and questionnaire B) are developed but they must have a linkage (in a sense of knowledge, skills and
behaviors) and then these assessments instruments are subjected on the same group. The result obtained from these groups are then correlated which can show the reliability of the test in regards of the alternate sets of instruments.
6. Inter - rater method of Reliability:
The Measures of the reliability about the different judges agree upon the decisions about the assessment is called inter rater method of rebility. The answers cannot effectively interpret by human observes and for that very purpose the inter-rater reliability is of utmost importance.
2.4 FACTORS AFFECTING RELIABILITY:
Reliability:
The degree or the extent of the similarities among the results obtained on several occasion or in other words it can be defined as the degree to which an assessment instruments elicit stable and consistent plethora results.
Reliability means consistency of measurement. The words of Ebel & Frisbie “The ability of a test to measure the same quantity when it is administered, to an individual on two different occasions by two different testers is called reliability”.
Reliability also called dependability or trust worthiness.
Reliability is the degree to which a test consistently measures whatever it measure.
Factors which affects the reliability:
The factors which badly affects the reliability are as under:
The examinee:
Fatigue burden, lack of motivation, carelessness.
Trait of Test:
Ambiguous items, poorly worded direction tricky questions in familiar format.
Conditions of test- taking and marking:
Poor examination condition, excessive heat or cold carelessness in marling, disregards or lack of clear standards for scoring, computational errors.
There are also some factors which affects on reliability, which are as under:
1. A very important factor influencing test reliability is the number of test items. That is the greater number of items in a test, the more reliable the test.
2. Other things being equal the narrower the rang of difficulty of the items of a test the granter the reliability.
3. Evenness in scaling is factor influencing the reliability of a test other things being equal a test every scaled is more reliable than a test that has gaps in the scale of difficulty of its items.
4. Other things being equal, inter-dependent items tend to decrease the reliability of a test.
5. The more objective the scoring of a test the more reliable is the test.
6. Chance in getting the correct answer to an items is a factor which lowers the test reliability.
7. Other things being equal, the more homogenous the material of a test the greater its reliability.
8. Other thing being equal, the more common the experiences called for in a test are the members of the group taking the test more reliable the test.
9. Other things being equal the same test given late in the school year (i.e. after covering the unit in the class) is more reliable that when given Carly in the year (i.e. without teaching the unit).
10. Other things being equal, each, question in a test lower the reliability of test. A test answered by the systematic relall or recognition of orderly facts or experience is more reliable than a test answered by sudden insight because of novelty.
11. Lengthy items lower the reliability because certain factors in the item will be over or under estimated.
12. Inadequate or faulty directions, failure to provide suitable illustrations of the task lower the reliability.
13. Strange or unusual words of items lower the reliability.
14. The accuracy with which a test is timed is an important factor in test reliability.
15. Difference in incentive and effort tend to make tests unreliable.
The appeal of a test is stronger with some individuals than with others, and is stronger with an individual at one time than at another.
16. Accidents occurring during the examination such as breaking a pencil, running out of link, or defective test booklets influence the reliability of the test. Outside disturbances also lower the reliability.
17. The interval between the test and retest is important for reliability estimate.
18. Cheating in the examination is another factor which lowers the reliability because the score of the individual may increase or decrease unduly.
19. Illness, worry, excitement though less important still they influence the reliability of the test.
References
Murad Ali Katozai 1st Edition, June, 2013 Measurement and Evaluation.
Dr. Mohammad Nooman & Obaid Ullah 1st Edition June 27th 2013 A Manual of Educational & Social Science and Research Methodologies.