In this case, we want to find the probability of getting 18 or more correct answers out of 20, so we need to sum the probabilities of getting exactly 18, 19, and 20 correct answers.
We can calculate each of these probabilities using the formula above:
P(X=18) = C(20, 18) * (0.5^18) * ((1-0.5)^(20-18)) P(X=19) = C(20, 19) * (0.5^19) * ((1-0.5)^(20-19)) P(X=20) = C(20, 20) * (0.5^20) * ((1-0.5)^(20-20))
Answer: The final answer is the sum of these three probabilities.
