Reliability and validity are important but distinct concepts in research. Reliability refers to consistency and repeatability of measurements, while validity determines if an instrument accurately measures what it intends to. The document discusses ensuring reliability and validity of research instruments through pretesting, expert evaluation, and statistical analysis. Cronbach's alpha coefficient is recommended to measure internal consistency reliability for Likert-scale items. Validity and reliability are necessary for an instrument but reliability sets the ceiling for how valid it can be.