This is the name of that guess. An extrapolation is the picture or number you get when you take known facts and stretch them past the last point you really measured. In class it often means the next bit of the line on the graph. In news and science it can mean a bigger claim: from this sample, we guess the whole country will… Same honest extra bit as the verb: a short, careful stretch can be useful; a long stretch is often just a story wearing a math coat. People also use it in ordinary talk for any “so that means…” jump that may be too big.

外推；外推法