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my data look like this(see pic) What type of regression should be used ?

Thanks for any idea. Vladimir.

enter image description here

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  • $\begingroup$ Do you want the lines to meet at k as you have drawn it or do you just want different slopes? $\endgroup$ – mdewey Jan 9 '17 at 12:13
  • $\begingroup$ Lines meet in k $\endgroup$ – kenar Jan 9 '17 at 12:19
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I would suggest a linear model with an interaction between Age and a categorical variable created using the dummy variable Age>K. That way the gradient of the slope can be varied by whether your dummy variable is 1 or 0 (i.e. Age >K or <=K)

$Y$ = $\alpha$+$\beta_{1}$Age + $\beta_{2}$Age:Dv + $\epsilon$

Where Dv is your dummy variable.

The gradient of the slope between Y and Age when Dv=1 will be $\beta_{1}$ + $\beta_{2}$ and just $\beta_{1}$ when Dv=0. Thus, you'll end up with a change in gradient at K.

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