13. Incorrect. The answer is true, not false. Let X be a random variable which represent the number of rocks with copper extracted at random. Let N be the number total number of rocks in the sample. M is the number of rocks with copper. N - M is the number of rock with lead. “n” is the sample taken at random

 

N = 11, M = 6, N - M = 11 - 6 = 5, n = 4.

 

The scenario satisfies the requirements of a hypergeometric experiment, for the probability distribution function of X is:

 

 

The expected value of this distribution is: E[X] = n[M/N]

 

The requested probability is P[X=3] =  ≈ 30.30%.

 

The expected value is E[X] = 4*(6/11) = 24/11 = 2.18 ≈ 2.