(7) Establishing the Validity of the Questionnaire

• validity - a research instrument is considered valid if it measures what it supposed to measure
• types of validity:

  1. face validity
  2. content validity
  3. concurrent validity
  4. construct validity
  5. predictive validity
• face validity - also known as "logical validity". It calls for an initiative judgement of the instrument as it "appear". Just by looking at the instrument, the researcher decides if it is valid.
• content validity - meets the objectives of the study. It is done by checking the statement of questions if this elicits the needed information. Experts in the field of interest can also provide specific elements that should be measured by the instrument
• construct validity - it refers to the validity of instruments as it corresponds to the theoretical construct of the study. It is concerning if a specific measure relates to other measures.
• concurrent validity - when the instrument can predict results similar to those similar to those similar tests already validated, it has concurrent validity.
• predictive validity - when the instrument is able to produce results similar to those similar tests that will be employed in the future. This is particularly useful for the aptitude test.
• reliability - refers to the consistency of the measures or results of the instruments
• types of reliability:

  1. test-retest reliability
  2. equivalent forms reliability
  3. internal consistency reliability
• test-retest reliability - it is achieved by giving the same test to the same group of respondents twice. The consistency of the two scores will be checked.
• equivalent forms reliability - it is established by administering two identical tests except for wordings to the same group of respondents
• internal consistency reliability - it determines how well the items measure the same construct. It is reasonable that when a respondent gets a high score in one item, he will also get one in similar items.
• Three ways to measure the internal consistency reliability

  1. split-half coefficient
  2. cronbach's alpha
  3. kuder-richardson formula