SOLUTION: I keep getting told my answer is incorrect for this problem, please help! 20% of people own 3 or more cars. 100 households are selected. X= the number of households with 3 or more

Question 367187: I keep getting told my answer is incorrect for this problem, please help!
20% of people own 3 or more cars. 100 households are selected. X= the number of households with 3 or more cars. The variance of X is?
I submitted 20 and then re-did the problem and came up with 4.
Now I am told that 4 is also incorrect.
Please help!
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
20% of people own 3 or more cars. 100 households are selected. X= the number of households with 3 or more cars. The variance of X is?
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Binomial with n = 100 and p = 0.2
u = np = 2
std = sqrt(npq) = sqrt(2*0.8) = 0.4
---
Variance of X = 0.4^2 = 1.6
=====================================
Cheers,
Stan H.

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