A student studying for a vocabulary test knows the meanings of 16 words from a list of 20 words. If the test contains 10 words from the study list, what is the probability that at least 8 of the words on the test are words that the student knows? (Round your answer to three decimal places.)

Question

anonymous · Answer

P[ 8 q's known] 
= [from 10 known q's, choose 8]* 
[from 10 unknown q's, choose 2] / 
[from 20 total q's, choose any10] 

we want to find P[>=8] = P[8] + P[9] + P[10] 
= [ 10C8*10C2 + 10C9*10C1 + 10C10 ] / 20C10 

ans: 0.012