OP6798
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If X-B(12,0.2)

I need to find P(3≤X≤5)

P(3≤X≤5)= P(X≤5)-P(X≤2)=0.4223

I just don't understand why it's P(X≤2) because I thought X had to be greater than or equal to 3?
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Interea
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(Original post by OP6798)
If X-B(12,0.2)

I need to find P(3≤X≤5)

P(3≤X≤5)= P(X≤5)-P(X≤2)=0.4223

I just don't understand why it's P(X≤2) because I thought X had to be greater than or equal to 3?
P(X≤5) will give you the probability that X is 0, 1, 2, 3, 4 or 5.
P(X≤2) will give you the probability that X is 0, 1 or 2.

P(3≤X≤5) is the probability that X is 3, 4 or 5, so taking our second probability from our first will give us that.
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OP6798
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(Original post by Interea)
P(X≤5) will give you the probability that X is 0, 1, 2, 3, 4 or 5.
P(X≤2) will give you the probability that X is 0, 1 or 2.

P(3≤X≤5) is the probability that X is 3, 4 or 5, so taking our second probability from our first will give us that.
ahh I see, thank you so much
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