Line of best fit question

[dream chaser]

Hi Guys,

When a question asks you to draw a line of best fit, for eg. 2018 VCE physics Exam Q20(a), does the line have to start at (0,0) and end until you cannot draw the line in the graph(boxes given) anymore or does the line only start at the first data point and end at the last data point?

The solutions given in the VCAA examination report shows the line of best fit starting at the first data point and end at the last data point.

All replies will be much appreciated. Thanks 

[fun_jirachi]

Hi there!

I don't do VCE but I'm sure the process is much the same In general, you shouldn't force a line of best fit through the origin, even more so when it isn't a data point. Your line of best fit is the best fit for the data you actually have (excluding outliers) and should thus be roughly in the range of the first and last data points (unless they're also outliers). You also shouldn't force the line through the first and last data points (or any data point for that matter), unless your line of best fit actually passes through them Extrapolation of the line shouldn't really be required or done unless a result off the graph in a future question is needed via extrapolation; in this case extend the graph with a dotted line to indicate extrapolation. ie. realistically, your line should start and end in the range of the first and last data points

Hope this helps