Questionnaire Validation Made Easy - EuroJournals

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Questionnaire Validation Made Easy 173 Method The systematic and manual search methods were adopted to review the available literature. Our review is many based on a MEDLINE, PUBMED, GOOGLE SCHOLAR searches of articles published between 1987 to 2010 and also the reference list of these articles Results Some Reasons for the Lack of Good Quality Validated Questionnaires It is, at times, difficult to locate and obtain developed questionnaires (3) due to lack of scientific incentives (3), lack of criteria for good quality questionnaire (4) lack of “Gold standard” questionnaires (5) and ignorance of the importance of accurate measurements and lack of funds for the purpose of development and validation of questionnaire is also one of the contributory factors. Questionnaire Development and Validation There are two basic goals (6) in questionnaire design. The first is to obtain information relevant to the purposes of the survey and the second is to collect this information with maximal reliability and validity. The question before the researcher is that the questionnaire he is adopting will measure what it is supposed to measure and will do this in a consistent manner? Now, before we start discussing the answer to this question let us go through the definitions for and methods of establishing the validity and reliability of a questionnaire. (see appendix) Some Important Definitions, Scores and Methods (7a, 7b, 8, 9, 10) Validity Validity is the degree to which an assessment measures what it is supposed to measure. Known Groups Validity Known groups validity is a form of construct validation in which the validity is determined by the degree to which an instrument can demonstrate different scores for groups know to vary on the variables being measured. Longitudinal Validity Longitudinal validity is the extent to which changes on one measure will correlate with changes on another measure Concurrent Validity To validate a new measure, the results of the measure are compared to the results of the gold standard obtained at approximately the same point in time (concurrently), so they both reflect the same construct. This approach is useful in situations when a new or untested tool is potentially more efficient, easier to administer, more practical, or safer than another more established method and is being proposed as an alternative instrument. Construct Validity Reflects the ability of an instrument to measure an abstract concept, or construct. For some attributes, no gold standard exists. In the absence of a gold standard, construct validation occurs, where theories about the attribute of interest are formed, and then the extent to which the measure under investigation provides results that are consistent with these theories are assessed.
174 Suri Sushil and Verma N Content Validity Refers to the extent to which a measure represents all aspects of a given social concept. Example: A depression scale may lack content validity if it only assesses the affective dimension of depression but fails to take into account the behavioral dimension. Criterion Validity Examines the extent to which a measure provides results that are consistent with a gold standard. It is typically divided into concurrent validity and predictive validity Discriminant Validity Measures that should not be related are not. Discriminant validity examines the extent to which a measure correlates with measures of attributes that are different from the attribute the measure is intended to assess. Face Validity A form of content validity, face validity is assessed by having 'experts' (this could be clinicians, clients, or researchers) review the contents of the test to see if the items seem appropriate. Because this method has inherent subjectivity, it is typically only used during the initial phases of test construction. Reliability Reliability can be defined in a variety of ways. It is generally understood to be the extent to which a measure is stable or consistent and produces similar results when administered repeatedly. A more technical definition of reliability is that it is the proportion of "true" variation in scores derived from a particular measure. The total variation in any given score may be thought of as consisting of true variation (the variation of interest) and error variation (which includes random error as well as systematic error). True variation is that variation which actually reflects differences in the construct under study, e.g., the actual severity of neurological impairment. Random error refers to "noise" in the scores due to chance factors, e.g., a loud noise distracts a patient thus affecting his performance, which, in turn, affects the score. Systematic error refers to bias that influences scores in a specific direction in a fairly consistent way, e.g., one neurologist in a group tends to rate all patients as being more disabled than do other neurologists in the group. There are many variations on the measurement of reliability including alternate-forms, internal, inter-rater agreement, intra-rater agreement, and test-retest Test-retest Reliability A way of estimating the reliability of a scale in which individuals are administered the same scale on two different occasions and then the two scores are assessed for consistency. This method of evaluating reliability is appropriate only if the phenomenon that the scale measures is known to be stable over the interval between assessments. If the phenomenon being measured fluctuates substantially over time, then the test-retest paradigm may significantly underestimate reliability. In using test-retest reliability, the investigator needs to take into account the possibility of practice effects, which can artificially inflate the estimate of reliability. Gold Standard A method of measuring reliability. Inter-rater reliability determines the extent to which two or more raters obtain the same result when using the same instrument to measure a concept.
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