# Probability Distribution: Only 40% of young trees planted will survive 1st year.

#### summerstiller

##### New member
HELP!!

Only 40% of young trees that are planted will survive the first year.
A school bought and planted 8 tree during the last holiday break.
Assuming independence (the survival of one plant does not affect others), calculate the probability that 6 trees will still be alive after one year.

#### tkhunny

##### Moderator
Staff member
HELP!!

Only 40% of young trees that are planted will survive the first year.
A school bought and planted 8 tree during the last holiday break.
Assuming independence (the survival of one plant does not affect others), calculate the probability that 6 trees will still be alive after one year.
Do this: $$\displaystyle (p+q)^8$$ - Expand it until you get all 9 terms.

AFTER you have done that, substitute p = 0.40 and q = 1 - p = 1 - 0.40 = 0.60 -- Do NOT add the terms.

You have just created tho Binomial Distribution for n = 8 and p = 040.

Note: Careful with the wording. "6 trees will be alive" may not mean EXACTLY 6 trees. It may mean AT LEAST 6 trees.

#### Jomo

##### Elite Member
HELP!!

Only 40% of young trees that are planted will survive the first year.
A school bought and planted 8 tree during the last holiday break.
Assuming independence (the survival of one plant does not affect others), calculate the probability that 6 trees will still be alive after one year.
I agree with tkhunny that the probability that 6 trees will still be alive after one year may not mean exactly 6, it may mean 6 7 or 8 will be alive. I personally would assume at least 6 will be alive.

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