The solution involves using the properties of binomial distribution:
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For a binomial random variable X ~ Bin(n, p):
- P(X=0)=(1−p)n=0.20
- P(X=1)=np(1−p)n−1=0.35
- E(X)=np=1.5
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From E(X)=np=1.5, we can substitute into P(X=1):
1.5(1−p)n−1=0.35
(1−p)n−1=0.35/1.5=0.2333
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We also have (1−p)n=0.20 from P(X=0)
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Dividing these two equations:
(1−p)n−1(1−p)n=0.23330.20
1−p=0.8571
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Now calculate variance:
Var(X)=np(1−p)=1.5×0.8571=1.2857≈1.3
Therefore, the variance is approximately 1.3, which corresponds to option D.