Explanation for Question 22 From the Math (Calc) Section on the Official Sat Practice Test 9
Question 21 reads the weight in pounds for 15 horses in a stable 2 were reported and the mean median range and standard deviation for the data were 3 found. The horse with the lowest reported weight was found to actually weigh 10 4 pounds less than it's reported. Wait, what value remains unchanged if the four 5 values are reported using the corrected weight? 6 Okay. So the best way to think about this one is to go through 7 them one by one and think about what each of these terms mean, 8 and whether it'd be affected by a difference in the lowest reported 9 weight. So the mean, 10 the mean is when you sum up all of your numbers and then divide 11 them by the number of occurrences. 12 So that would certainly be affected by a change in the lowest reported weight. 13 Your average would shift down because you're now going to be dividing a smaller 14 number on top. 15 The summation is going to be smaller over the same number of instances in 16 this case, the same number of 15 horses median 17 meeting is when you line all the numbers up for all of your, 18 your instances up from lowest to highest, 19 and then you pick the number in the middle. 20 So let's say you have just a sample of five horses. 21 Although obviously we're working with 15, he would pick the third horse in that 22 order. Now this is going to stay the same. 23 If the lowest reported weight is altered, 24 it's still is the lowest reported rate. So when finding the middle number, 25 the middle number is unchanged, but...