In this article, we will discuss theory about the validity and reliability of survey instrument prior to reliability. The validity is a test to measure the questionnaire content. There are three types of validity of which is:

1. The validity of contents

When a test use content validity, the items designed in a survey instrument should represent all possible indicators. The items designed as individually question allows other items broadly. Instantly, where a test tool to measure a person’s aptitude, the test tool will be difficult to define, a judgment of an expert may be able to provide an assessment of the relevance of the question items.

2. The validity related to criterion (criterion-related validity)

A measuring survey instrument is valid when it is able to measure its effectiveness in measuring criteria or indicators. In such validity, measurement or procedure will be measured by the value that has been proven valid or reality on the ground. An example, the test validity of written test for a driver, the test can be valid if the driver able to drive properly in the reality.

Test the validity of the criteria can be divided into two groups.

a. Concurrent validity

Is a validity test for survey instrument in which the criteria is similar with the benchmark. An example examines level of depression: a test has concurrent validity if it is to measure the level of depression that is being experienced by the participant. Simply, it able to measure the object in different time.

b. Predictive validity

While, predictive validity measures after testing. An example is the aptitude test, which helps measure the likelihood that someone is going to be successful on a carrier or a particular job. Researchers will only know after the study subjects underwent their work.

3. Construct Validity

Meanwhile, A validity test of survey instrument has construct validity if it is able to measure the relationship between predictions of the theoretical and empirical value.This construct validity measures the fit between the theoretical concept with more specific measurements items to measure the construct. While, Test intelligence is one example for testing the construct validity test. Finally, Researchers need to define variable then make specific measurements reflecting its latent variable.

Reliability

Reliability is consistency of research instrument when measured in different times or different subjects. Occasionally, two assessors conduct an instrument test and comparing the results. Whether it is similar, reflecting reliability. Likewise, a tools compared in different time. Consistent results mean the reliability of tool.