Binomial Probability

  • #1

Homework Statement



For a certain species of bird, there is a chance of three in five that a fledgling will survive. From a brood of ten chicks, find the chance that more than one will survive.

Let p = survival chance = 3/5
Let q = non-survival chance = 2/5

P(less than one will not survive) = P(more than one will survive) = 0.006047 + 0.040311

This answer is wrong, however, as my textbook is answer says it is about 0.9989 or something similar to that. I know how to get that answer through using powers (1-0.4^10) but I don't understand how I didn't get the same answer from the table because I have used that method a lot with many other questions and I does work. Perhaps someone could explain what I have done wrong with me?
 

Answers and Replies

  • #2
99
0
P(more than one will not survive) = 1 - P(none will survive) - P(only one will survive)
 
  • #3
P(more than one will not survive) = 1 - P(none will survive) - P(only one will survive)
I thought it was P(more than one will survive)?
 
  • #4
99
0
I thought it was P(more than one will survive)?
Oops, my bad. If that's the case then the formula should be:
P(more than one will survive) = 1 - P(none will survive) - P(only one will survive) = 0.9983.
 
Last edited:
  • #5
Oops, my bad. If that's the case then the formula should be:
P(more than one will survive) = 1 - P(none will survive) - P(only one will survive) = 0.9983.
Thanks.

However, would it still work for P(less than one will not survive)?
 
  • #6
99
0
Thanks.

However, would it still work for P(less than one will not survive)?
I think you should use P(less than two will not survive)?

P(more than one will survive) = 1 - P(none will survive) - P(only one will survive) = 0.9983.
Use p = 0.6 and q = 0.4

OR
P(less than two will not survive) = P(none not survive) + P(one will not survive) = 0.9983
Use p = 0.4 and = 0.6
 
  • #7
I think you should use P(less than two will not survive)?

P(more than one will survive) = 1 - P(none will survive) - P(only one will survive) = 0.9983.
Use p = 0.6 and q = 0.4

OR
P(less than two will not survive) = P(none not survive) + P(one will not survive) = 0.9983
Use p = 0.4 and = 0.6
Oh, thank you, I realise what I did wrong with my method. I did not include one will not survive in the second option.
 

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