Probability of contracting an STD in 4 sexual encounters

  • Thread starter Thread starter helpmeplzzz
  • Start date Start date
  • Tags Tags
    Probability
Join the discussion
Registration is free. Start your own thread to ask a follow-up.
Sign up Log in
1 reply · 2K views
helpmeplzzz
Messages
8
Reaction score
0

Homework Statement


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?



Homework Equations



Something with combinations maybe?

The Attempt at a Solution



I thought you would just add up the probability of the event happening for each trial, but that would give me 100% which isn't right.
 
Physics news on Phys.org

Discussion

helpmepleasezz said:

Homework Statement


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?



Homework Equations



Something with combinations maybe?

The Attempt at a Solution



I thought you would just add up the probability of the event happening for each trial, but that would give me 100% which isn't right.

Something simpler. What is the complementary event to "getting STD from at least one encounter"?