how to use multiple regression

[Guest]

Please can anyone help me solve this problem.

Use linest function to estimate what A,B,C & D will be, Compare them.

Y= a+bx+cx^2+dx^3

assum x=0, x=1, .................. x= 100

Calculate the corresponding value of Y. Choose any coefficient for the
constant.

Thanks and regards,
Dave

 

[Conrad Carlberg]

As written, your post is a little puzzling.

To use LINEST() you're going to need to start with both a series of X values
and a series of Y values. So you won't "Calculate the corresponding value of
Y," but you can use the regression coefficients and the constant to get
estimates of Y. If what you're really after is the Y estimates, the TREND()
function is more straightforward than LINEST() because it calculates the
equation and applies it to your X values to return the Y estimates. But if
you use LINEST(), and assuming you have Y in column A, X in column B, X^2 in
column C and X^3 in column D, start by selecting a blank range four columns
wide and five rows high, type this formula:

=LINEST(A1:A100,B1100,,TRUE)

and array-enter it with CTRL-SHIFT-ENTER instead of just ENTER. You can also
square and cube X in the arguments:

=LINEST(A1:A100,B1:B100^{1,2,3},,TRUE)

What do you want to compare A,B,C & D to? Zero? Something else? Use the
standard errors.

You can force the constant to zero using LINEST's third argument but in
general it's a bad idea.

 

[Guest]

Thanks Conrad.
The equation is actually not written well x^2 means x squared and x^3 means
x cube.so the equation is

Y= a + bx + cxsquared + dxcube

 

[Conrad Carlberg]

The equation is actually not written well x^2 means x squared and x^3 means

x cube.so the equation is

Y= a + bx + cxsquared + dxcube

That much was clear.

 

[Jerry W. Lewis]

Conrad already explained how to fit a cubic polynomial with LINEST. An
alternative to using the LINEST coefficients to predict y values at 1 to
100 would be

=TREND(known_ys,known_xs^{1,2,3},ROW(A1:A100))

array entered.

Jerry