Using the STDEV Formula in Google Sheets to Calculate Standard Deviation. Tick the Trendline option. Check the Trendline box and the Show R2 box.
It goes down in some places and up in others.
But wait you may be saying that line is all jaggedy. It goes down in some places and up in others. Un-check the box that says Treat labels as text. Calculates the y-value at which the line resulting from linear regression of a dataset will intersect the y-axis x0.