Explanation for Question 21 From the Math (Calc) Section on the 2017 May Sat
Question 21 gives us a scatter plot and we're going to be using the 2 paragraph of, they give us, plus the, 3 our analysis of the scatterplot to determine what the right answer is. 4 So the question says, this kind of thought above shows the number of surveys 5 sent to and returned from people in 17 different neighborhoods. 6 I line up best fit for the data is also shown for the neighborhood 7 that had survey sent to 800 people, 8 which of the following is closest to the positive difference between the actual number 9 of surveys returned and the number predicted by the line of best-fit shown. 10 So let's really quickly look at our scatter plot. 11 The title of the survey sent to one from 17 neighborhoods and in our 12 X axis is the numbers of surveys sent or Y axis is the number 13 of surveys returned. So if they want the 14 neighborhood that had 800 surveys sent, 15 we know that it's going to be on this line right here. 16 Now it asks us for the positive difference between the actual and predicted values. 17 So whenever you have a line of best fit, the line of best fit 18 is going to give you the predicted values and the actual points. 19 Those are the data values. Those are the actual values. 20 So on the 800, 21 if the Y is a returned, we know that this is going to be 22 our actual cause. It's the actual dot. 23 And then this is going to be our predicted because it's the line of 24 respite. This, 25 if we go across the line, we know it's at 600 and then this, 26 we can kind of estimate, but it's about halfway between 400 and 500. 27 So we can say it's four 50. So they want to know the positive 28 difference. So we just subtract 600 minus four 50, 29 and we got one 50 or a.