Mike D. answered • 08/25/20

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Vinu

- You can choose 7 students from 30 in 30 C 7 ways = 2035800 ways (30 ! / 23 ! 7 !)

(a) If A,B,C are in the team 3 places are taken. You can choose the other team members in 27 C 4 ways = 17550 ways. So probability = 17550 / 2035800 = 0.0086

(b) Well 17550 ways include all three. So how many will not use all three (use the 2035800 and 17550).

- Well you need p (63<X<73) = p ( (63-48)/9 < Z < ((73-48)/9) = p (1.67 < Z < 2.78). So use a table of areas under the standard normal - find the area when Z = 2.78 and take away the area when Z = 1.67

- For (3) you will get approximately the same answer. Binomial distribution gives exact answer, normal approximation gives a good approximation (there will be a small error).

Mike

Vinu P.

thank you for your help!08/25/20