Turn on thread page Beta
    • Thread Starter
    Offline

    0
    ReputationRep:
    I have a question from a solomon paper...maybe I am just being incredibly dumb, but I don't get the right answer to question 5)a)ii).
    What I don't understand is why P(X>5) for probability 0.65, the same as P(x<5) for prob 0.35. ...Why is it not p(x<=5)?
    Thank you.
    Attached Images
     
    Offline

    6
    ReputationRep:
    For this question, it asks the probability of more than five, which is equal to 1-probability of it being less than or equal to five....the binomila tables show
    P(x«X), so up to, and equal to, 5
    • Thread Starter
    Offline

    0
    ReputationRep:
    This is hard to explain but:
    My tables only go up to 0.5...so I can't get 0.65.
    If that is not what you meant, and you meant to use 0.35 as a probability, then for some reason the answer is not 1- P(X<=5).
    Also for the sake of this argument lets assume that we have to use the tables.
    Offline

    6
    ReputationRep:
    aha, I see the question, right, the probability of more than 5 being decreased in price is the same as the probability of less than or equal to 5 increasing in price, which uses the 0.35 probabilty (this is because the overall sample is 10) ....so is .9051 the correct answer?
    • Thread Starter
    Offline

    0
    ReputationRep:
    The actual answer is 1-P(X<=4) with a probability of 0.35.
    I'm glad it's not just me that is getting confused by this...
    Offline

    6
    ReputationRep:
    It is p(x<=4) yes, my bad lol, forgot 10 counts as zero >.<, but 1-probability? ..that I am confused about..
    • Thread Starter
    Offline

    0
    ReputationRep:
    whoops, you are right not 1-probability...but is there any chance you could explain what you mean by 10 counts as zero?
    Offline

    6
    ReputationRep:
    Increasing in price ........Decreasing in price
    .........0...................... .........10.................
    .........1...................... ..........9.................
    .........2...................... ..........8................
    .........3...................... ..........7................
    .........4...................... ..........6................
    .........5...................... ..........5.................
    .........6...................... ..........4................
    .........7...................... ..........3...................
    .........8...................... ..........2................
    .........9...................... ..........1.................
    .........10..................... ..........0...............



    So 10 of them increasing price is the same as 0 of them decreasing price, and vice versa...so as you can see, the probability of more than 5 decreasing in price is the same as 4 or less increasing in price
    • Thread Starter
    Offline

    0
    ReputationRep:
    ah ok, much clearer thank you.
 
 
 
Turn on thread page Beta
Updated: June 21, 2005
The home of Results and Clearing

1,021

people online now

1,567,000

students helped last year

University open days

  1. Keele University
    General Open Day Undergraduate
    Sun, 19 Aug '18
  2. University of Melbourne
    Open Day Undergraduate
    Sun, 19 Aug '18
  3. Sheffield Hallam University
    City Campus Undergraduate
    Tue, 21 Aug '18
Poll
A-level students - how do you feel about your results?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.