p = 0.25 n = 1000 standard error, SE = sqrt(p(1-p)/n) SE = sqrt(0.25(1-0.25) / 1000) = 0.0137 . proportion of flights within 3% = P(-0.03/0.0137 = P( (-0.03 / 0.0137) Solution p = 0.25 n = 1000 standard error, SE = sqrt(p(1-p)/n) SE = sqrt(0.25(1-0.25) / 1000) = 0.0137 . proportion of flights within 3% = P(-0.03/0.0137 = P( (-0.03 / 0.0137).