(2) Let the frequency of 1 group be k, and according to the meaning of the question, k+2k+3k+4k =1,k= 1 12.
∴ The frequency of the fifth group is: 1 12 ×2= 1 6.
∴ Total number of students sampled: 10÷ 1 6 =60 (persons)
That is, the sample size: 60 people;
(3) According to the meaning of the question, the frequency of the fifth group can represent the overall eugenic rate.
∴ eugenic rate:1.6×1.00% ≈1.7%.