The Solution:
Given:
The probability that a person is a college graduate is:
[tex]P(G)=0.33[/tex]The probability that a person is not a college graduate is:
[tex]P(G^{\prime})=1-P(G)=1-0.33=0.67[/tex]The probability that exactly 7 are college graduates.
Applying the binomial expansion theory, we get:
[tex]P(exactly\text{ 7})=^{20}C_7(0.33)^7^(0.67)^{(20-7)}[/tex][tex]P(\text{ exactly 7})=77520(0.33)^7(0.67)^{13}=0.181127\approx0.1811[/tex]Therefore, the correct answer is 0.1811
