# discrete function help

• December 7th 2010, 08:17 PM
Brokensound723
discrete function help
$f(x)=(9/c)x^2$ for $x= 1,2,3,...,6
$

For an appropriate value of c, we can define $P(X=x)=f(x)$

Find c so the functions is a pmf

So the outcome space has 6 values and its bounded? I don't know I'm completely lost
• December 7th 2010, 08:33 PM
harish21
Quote:

Originally Posted by Brokensound723
$f(x)=(9/c)x^2$ for $x= 1,2,3,...,6
$

For an appropriate value of c, we can define $P(X=x)=f(x)$

Find c so the functions is a pmf

So the outcome space has 6 values and its bounded? I don't know I'm completely lost

since the distribution is discrete, the pmf sums up to 1

$\displaystyle \sum_{x=1}^{6} \dfrac{9}{c}x^2\;=\;1$

$\dfrac{1}{c}\displaystyle \bigg[\sum_{x=1}^{6} 9x^2\bigg]\;=\;1$

now find c
• December 7th 2010, 09:01 PM
Brokensound723
oh wow I'm a moron, Thanks for that I got it now haha