Standard deviation of response

[MahaRoho]

Homework Statement

I have to find the standard deviation

Relevant Equations

There are not any

 

[FactChecker]

Homework Statement:: I have to find the standard deviation
Relevant Equations:: There are not any

I would think that this is not good enough. What form does the model have? Is the model a linear model? Are there equations for the mean and variance of the model?

 

[MahaRoho]

The model is linear. The nominal values are the means of those parameters.
1. I need to know the standard deviation of a single variable that includes the covariance of that variable.
2. What is the value of correlation co efficient if the variables are fully correlated (I think it is 1), partially (0-1) and anti (0 to -1)?

 

[FactChecker]

The model is linear.

Then you should start by writing down the general form of a linear model and then translate the additional information into statements about that model.

The nominal values are the means of those parameters.
1. I need to know the standard deviation of a single variable that includes the covariance of that variable.

A single variable does not have a covariance, it has a variance.
CORRECTION: Although the covariance is defined as cov(X,Y)=E[(X-E[X])(Y-E[Y])], there is nothing that says that X and Y have to be different. If they are the same random variable, the covariance is the variance.

2. What is the value of correlation co efficient if the variables are fully correlated (I think it is 1)

Yes.

, partially (0-1)

Possibly. Some people would include the negative values (-1,1)

and anti (0 to -1)?

Yes. That is also called "negative correlation" and "inverse correlation". I call variables "correlated" even if it is negative and if I want to distinguish positive from negative, I call them "positively correlated" or "negatively correlated". But others might prefer other terminology. In any case, the term "correlation" or "correlation coefficient" includes both the positive and negative cases.

 

[MahaRoho]

Thanks a lot for the reply. Btw, I think I saw a formula on the internet like Covariance(x)=Standard deviation/ mean... Is that formula correct?

 

[FactChecker]

Thanks a lot for the reply. Btw, I think I saw a formula on the internet like Covariance(x)=Standard deviation/ mean... Is that formula correct?

No, that is not correct. But I have corrected my comment about the covariance in post #4.
The definition of covariance of random variables X and Y is cov(X,Y)=E[(X-E[X])(Y-E[Y])].

 

[Office_Shredder]

Maybe a good starting point is writing down what the definition of sensitivity is.