What value of a measurement must be available if the accuracy of a measurement is to be determined?

The answer is the correct value

To evaluate the accuracy of a measurement, the measured value must be compared to the correct value and you must compare the values of two or more repeated measurements

By doing this, you will have a set of standard to follow to make sure that the result of your research still placed within the scope of standards that accepted by experts in your field, which reduce the likelihood of your result to be considered as invalid.