In the next few posts, we’ll unpack some of the statistical terms that the GRE throws around. These terms can be seen as ways to answer two central questions:

1. What’s Typical?
2. What’s Possible?

In response to the question of "What's Typical?" we can find the median, mean, or mode of the data. These give you a sense of what the average value is, or what the most common value is; in short, they describe what a typical value might be.

And in answering "What's Possible?" we can find the range, quartiles, or percentiles of the data. These give you a sense of the possibilities and how the possibilities are distributed.

In later posts, we will give actual definitions of these concepts. But first, some overarching advice about learning these concepts.

There are four main ways you’ll get tested on these concepts.

1. Given some data, find the value of one of these concepts (e.g. the mean, median, range, etc.).
2. Given some data, alter the data in some way (e.g. by adding 10 to every value), and then find the value of one of these concepts.
3. Given some graph/chart, estimate the value of one of these concepts.
4. Answer some question about some concept's general properties (e.g. that the interquartile range is always less than or equal to the range).

Thus, you want to understand the formal definition well enough to do questions of the first and second types. But you also want to have some intuitive sense for the concepts, so that you can do questions that fall in the third and fourth categories.