t-values for averages

[teho]

I have data for 10 countries and I have calculated correlations across these countries portfolio returns.. Now I have t-values for these individual countries' correlations, but if I'd like to calculate averages, how can the t-value number be achieved? Obviously I can take an average of the correlation values themselves, but can the same be done for t-values as well? Thanks.

[teho]

any ideas?