This concept paper discusses three critical notions in a quantitative study: validity, reliability, and normality. Quantitative methods are used in the social sciences to study society and human behavior. Quantitative methods in social science include various fields, including economics, education, political science, public policy, psychology, and sociology. One of the research approaches used in quantitative study is a survey. The survey is a set of questions intended to gather insight into people's thoughts, feelings, and behaviors. An excellent survey instrument is achieved when it can fulfill the assumption of validity, reliability, and normality of the data. The validity of a survey instrument measures the extent to which it measures what it is supposed to measure. While the reliability of a survey instrument measures the extent to which the instrument is consistent in measuring a concept. Finally, the normality test helps determine that the data that has been collected is normally distributed or taken from a normal population. Good data can explain the results obtained from the study. A good measurement should have the property of isomorphism with reality and the value obtained from the measurement. Therefore, a measuring instrument is considered good when the results can accurately reflect the reality of the phenomenon to be measured.