Question 1182743
The 95% half-interval is z(0.975)*sqrt(p*(1-p)/n)
=1.96*sqrt(0.000316*0.999684/420065)
=0.0000274; add that and subtract it from 0.000323, p hat.
so the interval is (0.000296, 0.000350)
or (0.030%, 0.0350%)