The possible values of x are 0, 1, 2; ( 1)
And p (x = 0) = c 213c220 = 78190, and p (x =1) = c13c17c220 = 9/.
Then the distribution list of x is
And ex = 0× 78190+1× 9190+2× 2190 = 710 (6 points).
(2) It can be known that the number of students who are excellent and not excellent in mathematics and excellent and not excellent in chemistry is as follows.
Excellent in mathematics, not excellent in mathematics, excellent in chemistry, 4 2 6, not excellent in chemistry, 3114, and 71320 in chemistry (8 points).
Then: χ 2 = 20× (4× 1 1? 3× 2) 26× 7×13×14 ≈ 3.778 > 2.706 (10)
Then, it can be considered that excellent chemistry scores and excellent mathematics scores are related on the premise that the error probability does not exceed 10%. (12)