t-test: tc(n-k-1, sig_level) … tc is larger for 2-tails test compared to 1-tail test. F-test: F(k, n-k-1, sig_level) … sigma related, 1-tail test, for multiple LR Chi2-test: Chi2(k, sig_level) … for Heterosk…(2nd regression, no easy stuff) DW-test: Dl_Du(k, n, sig_level) … for non-AR models. Except for DW test, reject the null hypothesis if V_test > V_critical.