Research process involves several steps and each step depends on the preceding steps. If step is missing or inaccurate, then the succeeding steps will fail. When developing research plan, always be aware that this principles critically affects the progress. One of critical aspects of evaluation and appraisal of reported research is to consider the quality of the research instrument. According to Parahoo (2006), in quantitative studies reliability and validity are two of the most important concept used by researcher to evaluate the quality of the study that is carried out. Reliability and validity in research refer specifically to the measurement of data as they will be used to answer the research question. In most cases, the instrument that measures the variable is the central issues in determining the reliability and validity of the data. Whatever data collection method is used, the intent must be accuracy and the result of the research is depend on the consistency, stability and repeatability of data collection instrument or in other word its reliability.
In addition to reliability, researcher need to know if the measurement technique used to collect data actually measures what it is supposed to measure; in other word is it a valid technique?. Estimating the degree to which an instrument is valid and reliable is a critical step in the research process because this determines how much weight can be placed on the result (Wood & Rose-Kerr, 2006). The concept of reliability and validity will be discussed as they ultimately will influence the data analysis and the final report.
The reliability of research instrument is a major criterion for assessing its quality. An instrument’s reliability is the consistency with which it measures the target attribute. According to Polit & Beck (2008), the definition of reliability is the accuracy and consistency of information obtained in study. Supported by Parahoo (2006),...