used for two different questions. We’ll talk more about sets of questions later in this chapter.
The SAT might even have a question that tests more than one of these statistical concepts at the same time.
Take it one step at a time and use Process of Elimination when you can.
23.
The grams of precious metals in recycled catalytic converters were measured for a
variety of automobiles. The data is presented in the table above. If the lowest data
point, 1 gram, and highest data point, 17 grams, are removed from the set, which of the
following quantities would change the most?
A) Mode
B) Mean
C) Range
D) MedianHere’s How to Crack It
Start by evaluating the easier answer choices and save mean for last. The mode of the current list is 6, and
removing 1 and 17 from the list won’t change that. Eliminate (A). The range is the difference between the
smallest number and the largest number on the list. Right now, the range is 17 – 1 = 16. If those extremes
are removed from the list, the new range is 15 – 2 = 13, and the range changed by 3 units. Keep (C) for
now. The median is the middle number in the list, or the average of the middle two numbers. Currently,
both middle numbers are 9, so the median is 9. This won’t change if 1 and 17 are removed, so eliminate
(D). The mean of a list is not likely to change dramatically with the removal of the numbers at the
extremes, so (C) is likely correct. To actually evaluate the mean, you need to add up all the numbers on
the list and divide by the number of items in the list. For the current list, the total is 152 for the 18 items,
so the average is 8. 44 . To find the new total if 1 and 17 are removed, don’t re-add everything; just
subtract 18 from the previous total. The new list will have only 16 items, so the new average is 8.375.
This is only slightly different than the previous mean, so eliminate (B) and choose (C).