Line of best fit for maths IA

[YourPrincess]

Is a line of best fit curved or straight?

I mean I know both of them have to be as close to the points as possible but for my IA I need it to linear but the points are a bit curved. Can I still use it as a linear or do I have to make it exponential? 

 

[Vioh]

Usually, you can compare the lines of best fit using the R² values (which you can easily get from typical graphing software like Excel). The closer the value is to 1, the better the line of best fit. Of course, it's a dilemma if both the linear line and the curved line have a high value for the R² (typically higher than 0.8). In that case, I'd recommend you to look at the theoretical relationship between the 2 variables in question. Does the theory from your textbook tell you that the relationship is linear, or does it tell you that the relationship must be exponential? In worst-case scenario, if the theory doesn't tell you anything, then you should choose which ever line that has the higher R² value.