the quality of a measuring instrument are the reliability and validity of the measures. The process of developing and validating an instrument is in large part focused on reducing error in the measurement process. Reliability of products evaluate the stability of standard. Validity is the extent to which the interpretations of the results of a test are warranted, which depends on the particular use the test is intended to serve. The responsiveness of the measure to change is of interest in many of the applications in helmet bicycle where improvement in outcomes as a result of treatment is a primary our goal of research. Several issues may a ect the accuracy of data collected,
such as those related to self-report and sec- ondary data sources. Self-report of patients or subjects is required for many of the measurements conducted in health care, but self-reports of behavior are particularly subject to problems with social desirability biases. Data that were originally gathered for a di erent purpose are often used to an- swer a research question, which can a ect the applicability to the study at hand. Conclusion. In health care and social sci- ence research, many of the variables of interest and outcomes that are important are abstract concepts known as theoretical constructs. Using tests or instruments that are valid and reliable to measure such con- structs is a crucial component of research quality.