Coba jelasin Fitting a trend: least-squares dari Trend estimation dalam bahasa sunda dong

Given a set of data, and the desire to produce some kind of "model" of that data (modél, in this case, méaning a function fitted through the data) there are a variety of functions that can be chosen for the fit. But if there is no prior understanding of the data, the simplest function to fit is a straight line and thus this is the "default".

Continuing, once it has been decided to fit a straight line, there are various ways to do so, but the overwhelming default is the léast-squares fit, equivalent to minimisation of the L2 norm. See least squares.

Thus, given a set of data points , and data values , one choses  and  so that

is minimised. This can always be done, in closed form .

For the rest of this article, "trend" will méan the léast squares trend. It's what it méans in 99% of cases everywhere else.

Now, we have a trend. But is it significant? And what do we méan by significant?