CHAPTER 4: QUALITIES OF A GOOD RESEARCH INSTRUMENT

ü  Validity

-          It means the degree to which a test or measuring instrument measures what it intends to measure.

ü  Types of Validity

·         Content validity – It means the extent to which the content or topics of the test is truly representative of the content of the course.

·         Concurrent validity – It is the degree to which the test agrees or correlates with a criterion set up as an acceptable measure.

·         Predictive validity – It is determined by showing how well predictions made from the test are confirmed by evidence gathered at some subsequent time.

·         Construct validity – It is the extent to which the test measures a theoretical construct or trait.

ü  Reliability

-          It means the extent to which a research instrument is dependable, consistent and stable.

ü  Methods in Testing the Reliability of a Good Research Instrument

·         Test-retest method – In this method, the same instrument is administered twice to the same group of subjects and the correlation coefficient is determined.

r_s = 1 – Z6D²

     N³-N

·         Parallel-forms method – Parallel or equivalent forms of a test may be administered of the group of subjects, and the paired observations correlated.

·         Split-half method – The test in this method may be administered twice, but the test items are divided into two values.

r_wt =   Z(r_t)

          1 + r_nt

·         Internal-consistency method – This method is used with psychological test which consist of dichotomously scored items.

Kuder-Richardson Formula 20

R_xx =  [N]     [SD² - ∑p_iq_i]

   N-1           SD²

ü  Usability

-          It means the degree to which the research instrument be satisfactorily used by teachers, researchers, supervisors and school managers without expenditures of time, money and effect.

ü  Factors to Determine Usability

1.      Base of administration. To facilitate the administration of a research instrument, instruction should be complete and precise.

2.      Base of scoring. It depends on the following aspects:

·         Construction of a test in the objective type.

·         Answer keys are adequately prepared.

·         Scoring directions are fully understood.

       3.  Ease of interpretation and application. Results of test are easy to interpret and                            

             apply if tables are provided.

       4.  Low cost. It is more practical if the test is low cost material-wise.

       5.  Proper mechanical make-up. A good research instrument should be printed  

             clearly in an appropriate size for the grade or year level for which the instrument

             is intended.