Probability of an event occurring at least once over n trials

  • #1
There is a 1 in 4 chance that on any given sexual encounter, Joe will contract an STD. If Joe has sex 4 times, what are the chances of him having an STD?
 

Answers and Replies

  • #2
pwsnafu
Science Advisor
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Hint: what is the probability of not contracting after 4 times?
 
  • #3
1-(.75*.75*.75*.75) = my answer?
 
  • #4
HallsofIvy
Science Advisor
Homework Helper
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Looks good.
 
  • #5
So how would you do it for the probability of Joe contracting an STD twice out of those 4 occasions?

I think you would have to do a combination for this?
 
  • #6
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As this is misplaced homework-type question, I am locking it. This thread was also posted in the Precalc section under Homework & Coursework.
 

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