The Definition of Validity

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a. The Definition of Validity

Validity means the appropriateness and accuracy of a measuring instrument tests. “There are two important elements in validity. First, validity shows the different kinds of degree which are perfect, enough, and low. Second, validity always relates to a specific purpose” Zainal Arifin, 2012: 247. According to Saifuddin Azwar 2012: 173-174, a test which has a high level of validity if it can perform its function as an instrument of measurement or give an accurate result according to the purpose of the measurement. Ngalim Purwanto 2009: 137 also stated that validity is the quality that shows the relation between a diagnosis and the purpose of the criteria in a learning process. Suharsimi 2009: 67-68 stated that validity can be divided into two categories. They are: 1 Internal Validity Internal validity is also known as “logic validity”. The word “logic” means reasonable. Internal validity is divided into two categories. They are: 1. Content Validity A test which has this kind of validity can clearly measure a certain objective which matches the learning materials. Content validity can be tried to be achieved in the process of test construction by elaborating the materials stated in the curriculum or the materials provided in the coursebook. How to elaborate the materials so that the validity of a test can be fulfilled will be discussed further in the process of constructing a test section. 40 b. Construct Validity A test which has validity of construct has the items that can measure every aspect of thinking which are mentioned in the specific in structional purpose. “Construction” in this case does not mean “building” that usually can be found in the engineering field, but it is a term which is made by psychologists through such a manner of describing a soul which consists of some aspects such as memory knowledge, understanding, and performance. 2 External Validity According to Anas 2011: 167, external validity is also called empirical validity. External validity comes from the observation in the field. On the ether hand, Suharsimi 2009: 66 stated that a test which has empirical validity if it has been tested empirically. There are two kinds of empirical validity. Those are: a Predictive Validity A test which has predictive validity can predict what will possibly happen in the future. b The Contrast-related Validity Test as an assessment tool is considered to have contrast-related validity when the test accurately shows any linear relationship between the first and the next test. The validity of the test items is calculated using point biserial correlation formula according to Suharsimi Arikunto 2009: 79: 41 t √ Where: Ypbi : The coefficient of biserial correlation Mp : The average score of the subjects with correct answer from the tested-validity item. Mt : The average of the total score St : The standard deviation from the total score P : The number of students with correct answer q : The number of students with wrong answer q=1-p According to Sumarna 2005:64, there is a certain limit to determine the validity of a test item. A test item that has positive and high correlation score will also yield a high level of validity. Items that have low correlation or zero score need to be validity-tested further. Items that have negative correlation from the total score are considered to be bad items as those have a contrast objective to that of the objective of the test.

b. The Definition of Reliability