The Amount of Money That Maria Earns in a Week $\$ 800$

The amount of money that Maria earns in a week is a random variable,X,with a mean of $\$ 800$ and a standard deviation of $\$ 20$ The amount of money that Daniel earns in a week is a random variable,Y,with a mean of $\$ 900$ and a standard deviation of $\$ 30$ The total,X +Y,of Maria's weekly income and Daniel's weekly income is a random variable with a mean of $\$ 800 + \$ 900 = \$ 1700$ and a standard deviation of $\sqrt { 20 ^ { 2 } + 30 ^ { 2 } } \approx \$ 36$ The calculation of the standard deviation requires the assumption that the incomes are independent of one another.Which of the following examples describes a situation in which that assumption may be violated? A: Maria and Daniel are married to each other.
B: Maria and Daniel work for the same company.
C: Maria and Daniel work in the same business.
D: Maria and Daniel were born in the same year.

A) A and B
B) A,B,C,and D
C) B,C,and D
D) B and C
E) A,B,and C