sysuse auto, clear
rename price y
rename wei   x1
rename mpg   x2
reg y x1 x2
scalar b1 = _b[x1]
mat v = e(V)
scalar t_b1 = b1/sqrt(v[1,1])
local df = e(N) - e(df_m)
scalar p_b1 = ttail(`df' , t_b1)*2

dis b1
dis t_b1
dis p_b1