How can you be sure that your measurement s are both accurate and reproducible?

A data can be reproducible if you get the same results even if you do two methods. This is a good representation that the measurements you've made are accurate because they are close to the exact or true values. In order to achieve this, you must minimize the errors by using reliable and high-precision instruments. Also, you must be extra meticulous of the readings that you take. It should be down to the last digit that you can possibly read. Don't round off as much as possible.