Answer to Question #298147 in Statistics and Probability for Vhal

Question

a certified public accountant (cpa) randomly selects 4 accounts for a group of 12 careful examination. The company being audited knows that 7 of the accounts contain - errors. what is the probability that all 3 accounts selected are error-free

Answer 1

Solution:

Assume total no. of accounts the company has 14. (It is missing in question).

Total no. of selected accounts = 3

No. of accounts contain - errors = 7

No. of accounts errors free = 14 - 7 = 7

Required probability $=\dfrac{^7C_3}{^{14}C_3}=\dfrac{35}{364}=\dfrac{5}{52}$