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icystrike
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Homework Statement
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Q1. In 10'000 typical young people, if 1% of non cannabis users develop psychosis, how many cannabis users would be expected to develop psychosis? Ans:28
Q2. The report states:
"About 20% of young people now report using cannabis"
"... individuals who used cannabis were 41% more likely to have any psychosis"
Given these two figures, and assuming that the incidence of pyschosis for reasons other than cannabis use is the same in both users and non users, what is the percentage of those with psychosis who have it due to cannabis use? (answer to nearest 1%). Ans: 8%
The Attempt at a Solution
1. P(cannabis ∩ psychosis) = P(cannabis) P(psychosis l cannabis) = 0.2 x 0.0141= 0.00282
Number of young cannabis users with psychosis = 0.00282 x 10000 = 28.2
2. P (cannabis l pyschosis) = P (cannabis ∩ psychosis) / P (psychosis)
= P (psychosis l cannabis) P (cannabis) / P (psychosis ∩ (cannabis ∪ non-cannabis))
= P (psychosis l cannabis) P (cannabis) / P [(psychosis ∩ cannabis) ∪ (psychosis ∩ non- cannabis)]
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