Normal values for a new test

Hello all,

I am testing a new measurement and I am trying to calculate the normal value of the new measurement. I had the measurement done be 6 observers and repeated that after 6 weeks to test intra and interobserver reliability. The variable has a normal distribution.
1- To get the normal values for the new measurement which data set to use ( I have the variable values for each observer on 2 occasions)
2- The normal value of the new measurement, is it the minimum and maximum value in all the measurements? or need to do something different?

Thank you in advance