Would a larger number of points in the line of best fit give a larger accuracy to the data?
I'm not sure what your question is. The data is the data and your analysis of it doesn't change its accuracy. I think what you meant to ask is whether retaining a subset of the data diminishes the accuracy of the fit. In short, the answer is "yes" but I don't see why you would want to deal with only a subset of the data since your computer can handle a large data set just as easily as a large one.
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