Answer: D. 0.8202
Explanation:
We would assume a binomial distribution for the number of horses presenting with West Nile virus. The formula is expressed as
P(x = r) = nCr × p^r × q^(n - r)
Where
x represent the number of successes.
p represents the probability of success.
q = (1 - p) represents the probability of failure.
n represents the number of trials or sample.
From the information given,
p = 15% = 15/100 = 0.15
q = 1 - p = 1 - 0.15
q = 0.85
n = 10
Therefore,
P(x ≤ 2) = P(x = 0) + P(x = 1) + P(x = 2)
P(x = 0) = 10C0 × 0.15^0 × 0.85^(10 - 0) = 0.1969
P(x = 1) = 10C1 × 0.15^1 × 0.85^(10 - 1) = 0.3474
P(x = 2) = 10C2 × 0.15^2 × 0.85^(10 - 2) = 0.2759
P(x ≤ 2) = 0.1969 + 0.3474 + 0.2759
= 0.8202