Question 1171771
np and n(1-p)>10 so can
95% CI half-interval is z*sqrt(p*(1-p)/n)=1.96*sqrt(0.1*0.9/400)=0.0294
the 95%CI is (0.0706, 0.1294)
the 90th CI uses 1.645 for z and the SE is 0.0247 so the interval is (0.0753, 0.1247)

Draw the normal distribution emphasizing -2,-1.96,-1.645, -1, 0, 1,1.645, 1.96, and 2.