Given that an event is successful 1 out of every 5 attempts, you can determine that the probability of that event is:
[tex]P(A)=\frac{1}{5}[/tex]Let be "A" the event.
By definition, the probability of the complement of an event can be calculated by subtraction the probability of the event from 1:
[tex]P(A^{\prime})=1-P(A)[/tex]Therefore, substituting the probability of the event A into the formula and evaluating, you get:
[tex]P(A^{\prime})=1-\frac{1}{5}=\frac{(1)(5)-1}{5}=\frac{5-1}{5}=\frac{4}{5}=0.80[/tex]Hence, the answer is: Last option.
