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Whether attempting a qualitative or quantitative study, scientific research depends on the study design, identifying the target population, establishing the appropriate methodology, choosing data collection methods and analysis procedures that ensure the validity of the study and reliability of results. Flawed research methodologies result in measurement error, which is the difference between the actual value and what has been measured. Although it is difficult to avoid random errors, any systematic errors (e.g., invalid and/or unreliable instruments) should be designed out.