Thanks a lot for your reply. This helps a lot. It seems to me that they have tried to incorporate the uncertainty range, which is a good thing, but one can have a poor implementation of a good idea, and it seems that is what has happened here.

The factor of 1.73 may be related to making the assumption of a uniform distribution, as explained here: https://www.itl.nist.gov/div898/handbook/mpc/section5/mpc541.htm

There are serious shortcomings in the implementation:

1. The default output one gets does not reflect the mean or the range or the scatter of the distribution. One gets 0 and 1, which are very poor approximations.

2. If one tries to get the best estimate value using, for example, the N function in your reply, one gets the mean of the minimum and the maximum (0.0485 for lithium-6). Normally, the value used for the best estimate for the abundance of lithium-6 is about 0.0759 (the value printed in previous versions), which probably means that the underlying distribution is not symmetric, but this seems to be ignored in the new implementation.

Anyway, thanks a lot again for your input. In a sense, you have put my suspicions on a firmer basis. I really feel I cannot use the new database for any serious calculations.

Best,

Otto Linsuaín