How to find the 90% Confidence Interval?

I am given X1...X3 value. I got my estimated coefficient from my data. Then i found my Mean response of my data. Now i need to find the 90% confidence interval of the mean response where i am struggling. I would appreciated anyone help in this regards.

x1=35; x2=45; x3=2.2; % given values

b0=158.4913; b1= -1.1416; b2=-0.4420; b3=-13.4702; %Estimated parameters

EY=b0+b1*x1+b2*x2+b3*x3; % Estimation of mean response

Vm=tinv(0.95,n-P); % n-p is the degree of freedom (46-4=42)

I believe the variance of the mean response would solve the problem? but how?

Answer 1

[Star Strider]

I do not understand what you are doing with the data in your post (I assume you have a matrix of x values at at least a vector of y values).

Since you have the Statistics Toolbox, do your regression using the regress function. It will give you your confidence intervals as part of its normal output (in the documentation, the ‘bint’) variable).