Probability Theory - conditional

In summary, the probability that a tick carries both Lyme disease and human granulocytic ehrlichiosis is 10% given that the tick has either Lyme disease or HGE.
  • #1
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Question:
Deer ticks can carry both Lyme disease and human granulocytic ehrilichiosis (HGE). IN a study of ticks in the Midwest, it was found that 16% carried Lyme disease, 10% had HGE, and that 10% of the ticks that had either Lyme disease or HGE carried both diseases.

(a) What is the probability P[LH] that a tick carries both Lyme disease (L) and HGE (H)?

My Part:
I don't know how to interpret this problem. Let me show my work thus far.

P[L] = 0.16
P[H] = 0.1

Now this last part, how do I interpret this..."10% of the ticks that had either Lyme disease or HGE carried both diseases."

Like this? given that the ticks had L or HGE, then the ticks that both diseases. So I would write this as:

P[LH | (L U H)] = 0.1

I don't know if this is right though. Any help would be awesome, thanks!

another thought I had was:
P[LH|L] + P[LH|H] = 0.1

This was the first one I did, but I got a probability of something like 0.006 which seems WAY to low.
 
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  • #2
P[LH | (L U H)] = 0.1 sounds correct.

It is the probability that a deer has L AND H knowing that it has L OR H. It is basically what the problem is saying but it speaks in percentage of a quantity instead of in probability.
 

Related to Probability Theory - conditional

1. What is conditional probability?

Conditional probability is the likelihood of an event occurring, given that another event has already occurred. It is denoted as P(A|B) where A is the event of interest and B is the known event.

2. How is conditional probability calculated?

Conditional probability is calculated by dividing the probability of the intersection of the two events (P(A∩B)) by the probability of the known event (P(B)). This can be represented by the formula P(A|B) = P(A∩B) / P(B).

3. What is the difference between conditional and unconditional probability?

Unconditional probability is the likelihood of an event occurring without any prior knowledge or conditions. On the other hand, conditional probability takes into account a known event and calculates the likelihood of the event of interest occurring under that condition.

4. How is conditional probability used in real life?

Conditional probability is used in various real-life scenarios, such as weather forecasting, medical diagnosis, and risk assessment in insurance. It helps in making informed decisions by taking into account the known conditions or events.

5. What is the relationship between conditional probability and independence?

If two events A and B are independent, then the conditional probability of A given B (P(A|B)) is equal to the unconditional probability of A (P(A)). In other words, the occurrence of B does not affect the likelihood of A happening. However, if A and B are dependent, then P(A|B) ≠ P(A) and the occurrence of B does affect the likelihood of A happening.

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