Need to know if my answer are correct or no ?  TOPIC_SOLVED

Standard deviation, mean, variance, z-scores, t-tests, etc.

Need to know if my answer are correct or no ?

Postby zorro on Sun Jun 27, 2010 10:50 am

Question :
Suppose A and B are two events with P(A)=0.5 and P(A B)=0.8
i) For what value of P(B) would A and B be mutually exclusive
ii) For what value of P(B) would A and B be independent

Solution
i)
if P(A) = 0.5 and P(A B)=0.8 then

P(B) = P(A B) - P(A) = 0.8 - 0.5 = 0.3 (Is this correct ?)

ii) NO clue on how to solve it
User avatar
zorro
 
Posts: 28
Joined: Sat Jun 12, 2010 9:26 am

Sponsor

Sponsor
 

Re: Need to know if my answer are correct or no ?

Postby maggiemagnet on Sun Jun 27, 2010 11:02 am

Your first answer looks fine to me. For the second, what is the formula or rule for independent events? :thumb:
User avatar
maggiemagnet
 
Posts: 287
Joined: Mon Dec 08, 2008 12:32 am

Re: Need to know if my answer are correct or no ?

Postby zorro on Mon Jun 28, 2010 2:01 am

The rule of independent events ,

But how do i use this as i dont know the value of
User avatar
zorro
 
Posts: 28
Joined: Sat Jun 12, 2010 9:26 am

Re: Need to know if my answer are correct or no ?

Postby Martingale on Mon Jun 28, 2010 3:55 pm

zorro wrote:Question :
Suppose A and B are two events with P(A)=0.5 and P(A B)=0.8
i) For what value of P(B) would A and B be mutually exclusive


As stated there is no answer to this question. if it was worded ...


i) For what value of P(B) could A and B be mutually exclusive

then your answer is correct
User avatar
Martingale
 
Posts: 363
Joined: Mon Mar 30, 2009 1:30 pm
Location: USA

Re: Need to know if my answer are correct or no ?

Postby Martingale on Mon Jun 28, 2010 4:02 pm

zorro wrote:The rule of independent events ,

But how do i use this as i dont know the value of



We also have

User avatar
Martingale
 
Posts: 363
Joined: Mon Mar 30, 2009 1:30 pm
Location: USA

Re: Need to know if my answer are correct or no ?

Postby zorro on Tue Jun 29, 2010 1:42 am

Martingale wrote:
zorro wrote:The rule of independent events ,

But how do i use this as i dont know the value of



We also have



How should i use this in solving the 2nd question

ii) For what value of P(B) would A and B be independent.
User avatar
zorro
 
Posts: 28
Joined: Sat Jun 12, 2010 9:26 am

Re: Need to know if my answer are correct or no ?

Postby Martingale on Tue Jun 29, 2010 1:48 am

zorro wrote:
Martingale wrote:
zorro wrote:The rule of independent events ,

But how do i use this as i dont know the value of



We also have



How should i use this in solving the 2nd question

ii) For what value of P(B) would A and B be independent.


we have two equations equal to the same thing




and




thus



replace the values you know and solve for
User avatar
Martingale
 
Posts: 363
Joined: Mon Mar 30, 2009 1:30 pm
Location: USA

Re: Need to know if my answer are correct or no ?

Postby zorro on Wed Jun 30, 2010 2:53 am

so

P(A) + P(B) - P(A B) = P(A). P(B)

0.5 + P(B) - 0.8 = 0.5 P(B)

P(B) - 0.3 = 0.5 P(B)

P(B) = 0.5/0.3 (Is this correct?)
User avatar
zorro
 
Posts: 28
Joined: Sat Jun 12, 2010 9:26 am

Re: Need to know if my answer are correct or no ?

Postby Martingale on Wed Jun 30, 2010 4:50 am

zorro wrote:so

P(A) + P(B) - P(A B) = P(A). P(B)

0.5 + P(B) - 0.8 = 0.5 P(B)

P(B) - 0.3 = 0.5 P(B)

P(B) = 0.5/0.3 (Is this correct?)


How can P(B) = 0.5/0.3? That number is greater than 1!!
User avatar
Martingale
 
Posts: 363
Joined: Mon Mar 30, 2009 1:30 pm
Location: USA

Re: Need to know if my answer are correct or no ?

Postby zorro on Thu Jul 01, 2010 2:25 am

Martingale wrote:
zorro wrote:so

P(A) + P(B) - P(A B) = P(A). P(B)

0.5 + P(B) - 0.8 = 0.5 P(B)

P(B) - 0.3 = 0.5 P(B)

P(B) = 0.5/0.3 (Is this correct?)


How can P(B) = 0.5/0.3? That number is greater than 1!!



from my work can u please point out the mistake
User avatar
zorro
 
Posts: 28
Joined: Sat Jun 12, 2010 9:26 am

Next

Return to Statistics