SOLUTION: Trees planted by a landscaping firm have a 95% one-year survival rate, If they plant 15 trees in a park, what is the following probabilities: 1. All the trees survive one year.

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Question 1168491: Trees planted by a landscaping firm have a 95% one-year survival rate, If they plant 15 trees in a park, what is the following probabilities:
1. All the trees survive one year.
2. At least 13 trees survive one year.
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
the first is 0.95^15=0.4633 assuming independence.
At least 13 means 13,14,15
13 surviving is 15C13*0.95^13*0.05^2=0.1348
14 is 15*0.95^14*0.05=0.3658
The total is 0.9639
or 1-binomcdf(15,0.95,12)=0.9638, the difference due to rounding. The last is more accurate.