<ul><li>Criteria for Good Measurement : </li></ul><ul><li>Reliability : When the outcome of a measuring process is reproduciable, then the measuring instrument is reliable – Reliability provides stable measures at different times under different conditions – Eg. Coffee Vending Machine. </li></ul><ul><li>- However, poor data collection methods give rise to low reliability </li></ul><ul><li>- If the respondent do not understand the question, then it may not be reliable. </li></ul><ul><li>Methods to evaluate reliability : </li></ul><ul><li>Test – Retest Reliability : </li></ul><ul><li>If the result of a research is the same, even when it is conducted for the second or third time, it confirms reliability. </li></ul><ul><li>It is difficult to locate the same respondents and to obtain their co-operation for the second time </li></ul>
b) Equivalent form reliability : In this case two measurement scales of similar nature are to be developed. Eg. If the researcher is interested in finding out the perceptions of consumers on recent technologically advanced product. In this case develop two questionnaires with different questions but carrying the same meaning. Number of questions should be the same. Apply on the same respondents but at reasonable interval. Reliability can be tested by its correlation of the scores.
2) Validity : The ability of a scale to measure what it is intended to measure can be termed as the validity of the measurement. Eg. Students can complain about the validity of the exams stating that it did not measure their understanding of the topic, but only their memorising ability. Validity can be measured through several methods : a) Face Validity : It is the collective agreement of the experts and researchers on the validity of the measurement scale. b) Content Validity
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