The Wilson family had 8 children. Assuming that the probability of a child being a girl is 0.5, find the probability that the Wilson family had: at least 3 girls? at most 3 girls? Round your answers to 4 decimal places.
Given that, the Wilson family had 8 children. Assuming that the probabilitiy of a child being a girl is 0.5.
Let X be a number of girls among 8 children.
Here, X ~ Binomial (n = 8, p = 0.5)
a) We want to find, P(X ≥ 3)
P(X ≥ 3)
= 1 - P(X ≤ 2)
= 1 - [ P(X = 0) + P(X = 1) + P(X = 2) ]
= 1 - [ 0.0039 + 0.0312 + 0.1094 ]
= 1 - 0.1445
= 0.8555
Therefore, the probabilitiy that the Wilson family had at least 3 girls is 0.8555
b) We want to find, P(X ≤ 3)
(X ≤ 3)
= P(X = 0) + P(X = 1) + P(X = 2) + P(X = 3)
= 0.0039 + 0.0312 + 0.1094 + 0.2188
= 0.3633
Therefore, the probabilitiy that the Wilson family had at most 3 girls is 0.3633
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