Explanation for Question 25 From the Math (Calc) Section on the 2019 October Sat
And question 25. We're told that there's a dataset of 27 numbers that 2 has a mean of 33 and also a median of 33. 3 And then we add, um, by adding seven, 4 we create a new dataset where we add seven to each number from the 5 original set that is greater than the median. 6 And we subtract seven from everything that was below the median. 7 So I'll just create a real small example to show you what's happened happening. 8 Right. We know that really there's 27 numbers, 9 but let's pretend that there were only three numbers. 10 And if we had a mean and a median of 33, 11 maybe they could have been 33 32 and 34. 12 Now, if I'm adding seven to everything, that's greater than the median, 13 then I would be doing 34 plus seven, 14 which would give us 41. 15 And then if I'm doing subtracting seven, from everything that's lower than the median, 16 then I'm doing 32 minus seven. 17 And that gives me 25. So that's essentially what's happening here. 18 That's how we're changing the data values. Um, 19 and then it goes on to ask us, 20 which of the following measures does not have the same value, 21 right? And so we can kind of do this by looking at our example 22 here, since we're not changing the median at all, 23 right. It makes sense that the median should actually stay the same because here 24 in our set of three, right, we see our median is 33. 25 This should be a 33 now 37. And then here still, 26 our median is 33 because it doesn't change. 27 And we're also not changing how many numb...