Explanation for Question 20 From the Math (Calc) Section on the 2019 October Sat
Now for question 20, we given a plot with some, 2 some points and also align, right? And so it says that there's a scatter 3 plot with the line of best fit. 4 So right here is going to be the line of best fit. 5 And then it asks us of the following, which best estimates the amount, 6 which best estimates the amount by which the line underestimates the value of Y 7 when X is 50. So if we look here, 8 right, we want to see how much the line underestimates the actual 9 value when we have an X of 50. 10 So let's start here, let's start by finding where X of 50 is. 11 We see it's right here. Right? And so that means that the line is 12 about here, but the actual data point is here. 13 And just like we saw in the question, the line does in fact underestimate 14 the point, right? 15 Because the line is much lower than where the point actually is. 16 Now it looks like the point is actually at 65, 17 but the line estimates it to be closer to about 55. 18 Right. So right here would have been exactly or not 55, 19 but closer to maybe 46. 20 So the line says like 46 or 47. 21 Right. And so we just need to find the difference between these two values 22 and see what they're closest to, as far as our answer choices go. 23 So if we do 65 minus 47, 24 right, we can go ahead and do just a little bit of quick math 25 there, and that'll be eight. 26 We see that there were about 18 apart, right? And so you may not 27 have said 47, you said, okay, maybe that looks like 46 or 48, 28 but either way, you know, you're going to get 16, 17, 18, 19. 29 You're going to go to value in this range, which is closest to answer 30 choice D 18. 31 And so ultimately what we're showing with that 18 is that the distance between 32 the actual point and the line of best fit is 18 units.