1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Binomial Probabilities

  1. Sep 20, 2013 #1
    1. The problem statement, all variables and given/known data
    You are a real estate salesperson and you currently have 10 listings. Past experience has shown that you will sell approximately 70% of your listings. If sales are independent:

    What is the probability that you make exactly 8 sales?

    2. Relevant equations

    3. The attempt at a solution
    I was wondering why 70% would be used as the the probability for the event of interest... I thought the probability would be the probability of ONE listing that would sell and not 7/10 of your listings. Can someone explain?
  2. jcsd
  3. Sep 20, 2013 #2

    Ray Vickson

    User Avatar
    Science Advisor
    Homework Helper

    The 70% figure is a long-run average. It really means that the probability of sales is 0.70 per listed property.

    Sometimes problem posers want to sound more conversational and less formal, so instead of saying p = 0.7 per trial they say there is a 70% chance per trial, or sales = 70% of listings; that means 70% on average, not in any individual group of listings.
  4. Sep 21, 2013 #3


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    I think there's a little more to it than conversational usage. It is saying that your experience is that you sell 70% of your listings. That's a simple observation. From that you infer that your probability of selling a given listing (in the future) is 0.7. There are certain assumptions in that inference which might not in general be valid.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted