 # GRE Quantitative: Data Analysis – Numerical Methods for Describing Data

Recently, statistics has become an integral part of the Quantitative Reasoning section. Apart from the problems on mean or average, there is a high possibility of finding multiple questions on standard deviation, median, mode, and range. Hence, ignoring this section during your preparation for GRE can affect your score adversely.

Firstly, we should understand why people usually dodge this topic. When it comes to statistics even the savviest of test- takers cringe, but you can be the one to excel in this topic with utmost ease. Let us understand the topics one at a time so that it all comprises the syllabus of numerical methods for describing data of the data analysis in GRE quantitative reasoning section.

• Mean:Both mean and arithmetic mean can be commonly recognized by their alternate names of average in GRE exam. Irrespective of the name we use to call it, the methods of calculation are always the same that is add all the values and divide it by the number of terms. Undoubtedly you would have seen questions based on mean in your high school. Hence the formula can be represented mathematically as Mean= (Summation of all terms)(Number of terms)
• Median: For a group of numbers, to calculate the median, the middle term is taken as the median value, when the numbers are written in either descending or ascending order. Hence, it is easy to comprehend that for calculating median it is important for you first to rewrite the terms in either descending or ascending order. But what to do if there are two middle terms? in that case, which one to choose? Well, it is easy, if two numbers are appearing in the middle, simply take the mean of the two and this mean will give you the median value. For a list of consecutive numbers, you don’t need to break a sweat. Just add the first term and the last term and divide it by 2 and you will get the intermediate value. So the formula used can be Median= (First Term +last term)2
• Mode: For a group of numbers, the mode will be the number that has occurred most frequently. If more than one number is taut for first place in the race to befall the other, then don’t you worry the group will have multiple modes.
• Range:The range of a set of number can be calculated by taking the difference of the largest term and the smallest term.
• Standard Deviation: Even though standard deviation is the most complex concept of statistics luckily for GRE you will need only the basics. GRE won’t ask you to actually calculate the standard deviation as the formula is bit complicated and calculation can take a lot more time than anticipated. But you will be expected to know what standard deviation is. Standard deviation is a measure of how assorted out a group of values is. The more spread of the group, the larger will be its standard deviation.Apart from common numerical methods to identify data like mean, mode, median, range and standard deviation, there are other types of methods which are used. Two of the more famous numerical methods are percentiles and quartiles.
• Percentiles: They are mostly used with large datasets, ordered from the lowest to the greatest. The data is distributed into 99 groups starting from 0. For example, a data in the 90th percentile means that, that data is greater than 90% of the total data set. The percentiles are mostly used for distinguishing students in huge exams like GRE, GMAT, CAT.
• Quartiles: Quartiles on the other hand, are used with a much smaller data set, ordered from the greatest to the lowest. The data is distributed into 4 groups, with 3 quartile points. The points are arrived into by taking the median of the group of numbers. This technique is used by educational institutions to form the grade scale for a subject. The greater the number of grades on offer, the greater are the quartile points.

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