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0

$begingroup$

I have fitted some data with a normal and gamma distribution. But I need to find the expected value of my variable. For example is x is my data (mine is not normal) and fit them into a normal and gamma distribution. My expected value is not the same as the mean? Also for the gamma distribution the mean is alpha/beta which gives me the same as the mean.

x=rnorm(100)
m=mean(x)
v=var(x)
no=dnorm(x,m,sqrt(v))
gama=dgamma(x, ((m^2)/v),m/(v))

PS: But I think what my professor wanted me to do was: I was given a dataset of two variables and I needed to see which distribution fitted better, (it was a gamma), but after doing this the problem asked for the two distributions(Normal and gamma) to find the expected value. But I don't get if it has to be equal to the mean(x) in R. Or if I have to make an integral for this

PS2: I think for a simple way to ask. If I already fitted my data lets say to a normal(4,8) then my expected value isn't equal to 4? The same is for the gamma distribution, given alpha and beta, my mean isn't equal to alpha/beta?

probability

share|cite|improve this question

asked yesterday

Lexie WalkerLexie Walker

1597

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  There is no reason why your sample's average will exactly equal the distribution's mean (expected value). Usually it will be close to it, but not exactly the same.
  $endgroup$
  – Minus One-Twelfth
  yesterday
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @MinusOne-Twelfth Exactly, but this is the code that the professor gave us. So i don't know how to extract the expected value if those are the parameters.
  $endgroup$
  – Lexie Walker
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Given only a data set, you have no way of knowing (with certainty) the expected value of the underlying distribution. It sounds like maybe your prof. wants you to fit both normal and gamma distributions, and report the means of the two fit distributions.
  $endgroup$
  – David M.
  yesterday
  

  
  
  
  

add a comment | 

0

$begingroup$

I have fitted some data with a normal and gamma distribution. But I need to find the expected value of my variable. For example is x is my data (mine is not normal) and fit them into a normal and gamma distribution. My expected value is not the same as the mean? Also for the gamma distribution the mean is alpha/beta which gives me the same as the mean.

x=rnorm(100)
m=mean(x)
v=var(x)
no=dnorm(x,m,sqrt(v))
gama=dgamma(x, ((m^2)/v),m/(v))

PS: But I think what my professor wanted me to do was: I was given a dataset of two variables and I needed to see which distribution fitted better, (it was a gamma), but after doing this the problem asked for the two distributions(Normal and gamma) to find the expected value. But I don't get if it has to be equal to the mean(x) in R. Or if I have to make an integral for this

PS2: I think for a simple way to ask. If I already fitted my data lets say to a normal(4,8) then my expected value isn't equal to 4? The same is for the gamma distribution, given alpha and beta, my mean isn't equal to alpha/beta?

probability

share|cite|improve this question

asked yesterday

Lexie WalkerLexie Walker

1597

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  There is no reason why your sample's average will exactly equal the distribution's mean (expected value). Usually it will be close to it, but not exactly the same.
  $endgroup$
  – Minus One-Twelfth
  yesterday
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @MinusOne-Twelfth Exactly, but this is the code that the professor gave us. So i don't know how to extract the expected value if those are the parameters.
  $endgroup$
  – Lexie Walker
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Given only a data set, you have no way of knowing (with certainty) the expected value of the underlying distribution. It sounds like maybe your prof. wants you to fit both normal and gamma distributions, and report the means of the two fit distributions.
  $endgroup$
  – David M.
  yesterday
  

  
  
  
  

add a comment | 

$begingroup$

I have fitted some data with a normal and gamma distribution. But I need to find the expected value of my variable. For example is x is my data (mine is not normal) and fit them into a normal and gamma distribution. My expected value is not the same as the mean? Also for the gamma distribution the mean is alpha/beta which gives me the same as the mean.

x=rnorm(100)
m=mean(x)
v=var(x)
no=dnorm(x,m,sqrt(v))
gama=dgamma(x, ((m^2)/v),m/(v))

PS: But I think what my professor wanted me to do was: I was given a dataset of two variables and I needed to see which distribution fitted better, (it was a gamma), but after doing this the problem asked for the two distributions(Normal and gamma) to find the expected value. But I don't get if it has to be equal to the mean(x) in R. Or if I have to make an integral for this

PS2: I think for a simple way to ask. If I already fitted my data lets say to a normal(4,8) then my expected value isn't equal to 4? The same is for the gamma distribution, given alpha and beta, my mean isn't equal to alpha/beta?

probability

share|cite|improve this question

asked yesterday

Lexie WalkerLexie Walker

1597

$endgroup$

x=rnorm(100)
m=mean(x)
v=var(x)
no=dnorm(x,m,sqrt(v))
gama=dgamma(x, ((m^2)/v),m/(v))

share|cite|improve this question

asked yesterday

Lexie WalkerLexie Walker

1597

share|cite|improve this question

asked yesterday

Lexie WalkerLexie Walker

1597

asked yesterday

Lexie WalkerLexie Walker

1597

asked yesterday

Lexie WalkerLexie Walker

1597