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I have a scatter plot that I have drawn a line of best fit through in JMP. I want to know what equation to use to calculate the predicted y at specific points across the line. For example, if my x values range from 0 to 100 and I need to calculate the y value where x = 25 intersects the line of best fit, how would I go about doing that?

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  • $\begingroup$ The line has the form y=ax+b where a and b are the estimated parameters. Just plug in x=25 to get y=25 a +b. That point will be on the line of best fit (least squares line if that is the method you are using. Is this really what you meant? Perhaps you want the confidence bands? $\endgroup$ Nov 11, 2017 at 23:07
  • $\begingroup$ What estimated parameters are a and b? Y intercept and slope? $\endgroup$
    – Tye
    Nov 11, 2017 at 23:13
  • $\begingroup$ Yes a is the estimated slope and b is the estimated intercept. $\endgroup$ Nov 11, 2017 at 23:22

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If you're using Graph Builder, there's a "Show Equation" option in the lefthand properties panel for the regression element. Or you can use Launch Analysis from the red triangle which will open a full modeling report with parameter estimates and p-values.

Btw, there is a meta-page that lists software-specific Q&A resources since this forum tries to focus on general statistics issues.

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