Incorrect Trendline Linear Equation

[ossisuhonen]

Hi

I have problem with getting a correct equation in excel

x 0,98 0,985 0,99 0,995 1 1,005 1,01 1,015 1,02
y 0,97526 0,98207 0,98847 0,99444 1,00000 1,00513 1,00982 1,01408 1,01787

In picture can be seen the y value should be 1 when x is 1
but the equation 0.005331 * x + 0.971916 gives with the value of one result 0.977....

What is wrong?

[zbor]

You approximating non-linear curve with a linear one.
obviously, all points can't match (except for linear line).

You can use quadratic equation to be more precise:

Please Login or Register  to view this content.

[ossisuhonen]

I googled and found that for some reason excel line curves don't show the correct equation. I changed it to XY-scatter and got a result which gives very right the correct result. That is because of deviation of the points.

y = 1,0662x - 0,0676