random var. X is -1, 0, 1 w/ equal probability (check ans)

Standard deviation, mean, variance, z-scores, t-tests, etc.
User avatar
zorro
Posts: 28
Joined: Sat Jun 12, 2010 9:26 am
Contact:

random var. X is -1, 0, 1 w/ equal probability (check ans)

Postby zorro » Tue Jun 29, 2010 2:27 am

Question :
X is a random variable which takes 3 values -1,0,1 with equal probability i.e. P(x=-1) = P(X=0) = P(X=1) = 1\3
Find E(X) and Var(X)
Solution :
E(X) = 0 (is this correct?)

var(X) = 0 (is this correct?)

User avatar
Martingale
Posts: 350
Joined: Mon Mar 30, 2009 1:30 pm
Location: USA
Contact:

Re: random var. X is -1, 0, 1 w/ equal probability (check an

Postby Martingale » Tue Jun 29, 2010 3:53 am

zorro wrote:Question :
X is a random variable which takes 3 values -1,0,1 with equal probability i.e. P(x=-1) = P(X=0) = P(X=1) = 1\3
Find E(X) and Var(X)
Solution :


ok...

zorro wrote:E(X) = 0 (is this correct?)


Yes

zorro wrote:var(X) = 0 (is this correct?)


No

User avatar
zorro
Posts: 28
Joined: Sat Jun 12, 2010 9:26 am
Contact:

Re: random var. X is -1, 0, 1 w/ equal probability (check an

Postby zorro » Wed Jun 30, 2010 2:27 am

Please can u tell what is wrong


My work ........
E(X) = 0

1 = 0

2= 2/3

2 = 2/3

var(X) = 2 - 2 = 2/3 - 2/3 = 0

User avatar
Martingale
Posts: 350
Joined: Mon Mar 30, 2009 1:30 pm
Location: USA
Contact:

Re: random var. X is -1, 0, 1 w/ equal probability (check an

Postby Martingale » Wed Jun 30, 2010 4:48 am

zorro wrote:Please can u tell what is wrong


My work ........
E(X) = 0

1 = 0

2= 2/3

2 = 2/3

var(X) = 2 - 2 = 2/3 - 2/3 = 0



User avatar
zorro
Posts: 28
Joined: Sat Jun 12, 2010 9:26 am
Contact:

Re: random var. X is -1, 0, 1 w/ equal probability (check an

Postby zorro » Sun Jul 04, 2010 4:03 pm

Martingale wrote:
zorro wrote:Please can u tell what is wrong


My work ........
E(X) = 0

1 = 0

2= 2/3

2 = 2/3

var(X) = 2 - 2 = 2/3 - 2/3 = 0





Thanks !!! :clap:


Return to “Statistics”

cron