Statistics are extremely important in life. But, on the GMAT, you don't need to have the skills of an economist to crack problems. Generally, the test makers rarely provide problem solving questions related to stats, but they almost always provide data sufficiency questions related to stats.
So, knowledge of some rules is all you need to tackle most DS problems related to statistics.
The most common "rule" that you should become familiar with: what happens to a stat when you add a new parameter or subtract a new parameter? Does the mean change when you suddenly multiple the same number across individual parameters? What is the one thing that rarely changes?
I'll give you the answers to all these questions in just a second. But, first let us understand why we need to know this stuff. Basically, statistics problems are trickiest when they are combined with the Data Sufficiency format. You can't or shouldn't solve anything related to a DS problem, unless you want to waste a lot of time.
So, the alternative is to know certain "properties" related to statistics, in case the test makers decide to play statistical mind games with you.
Rule 1: Any time you add,subtract, multiple or divide anything with the individual components of a series, the Mean and Median change.
For example: Mean of 2,3,4 = 3 , but if we add 1, mean of (2+1,3+1,4+1) = 4
Notice: Mean increases by 1 as well!
Rule 2: Range and Standard deviation DO NOT change on addition or subtraction.
For example, Range in the above example was = 2. Even after addition of 1, the range still remained 2!
Rule 3: Range and Standard deviation DO CHANGE on multiplication or division.
For example, if we have original series as 2,3,4 and new series as 2x2,3x2,4x2 or 4,6,8 ...
Then, the range changes from 2 to 4!
Notice: Range increases by a factor of 2 as well.
Those are the 3 rules that you should know. The example given by me should be enough for you to remember these rules.
0 comments:
Post a Comment