Explanation for Question 9 From the Math (Calc) Section on the 2019 March Sat
So question nine says the scatterplot above shows the citrus production in 2 millions of metric tons in China from 2006 through 2014, 3 which of the following could be the slope of a line of best fit 4 for these data. So since the line of best fit is just a line 5 that estimates the average of all the data points in the graph, 6 I've gone ahead and drawn an estimation of what that would look like. 7 So it's going to look something like this line that I've drawn here now 8 to find the slope of this, we're just going to have to pick two 9 points on it and use the slope formula Y two minus Y one. 10 That's down here over X two minus X, 11 and that's going to give us an estimation of the slope. 12 So we're going to take this data point right here, 13 which looks like it's at about zero 18. 14 And then the second data point right here. 15 And that's at one 20. 16 So then all we have to do is put that into the slope 17 formula 20 minus 18 for the Y values 18 and one minus zero for the X values. 19 And that gives us two over one or about two. 20 So now looking at the answer choices, 21 since this was just an estimation, it's not going to be the exact slope 22 of the line. So we're just going to look for the answer choice. 23 That's the closest to that. And two point 12 is pretty close to the 24 estimation we found. And so from that, 25 we know that a is the correct answer.