GRE Data Interpretation  The Definitive Guide
Data Interpretation for the GRE General Exam consists of three questions in both quant sections of the test. Thus, there will be a total of six questions across both sections, and they will be placed in the same order.
Quote:
3 questions on data interpretation (Q68 was data interpretation)
from my guide
Shorter GRE  How score is calculated & the new exam pattern. I suggest you to have a look at this. Knowing the exam pattern will help you in your time management of the test. Turns out, it is also a strategy.
The threegrouped table and graph questions aren’t really more challenging than the other math questions, but they do take more time to sort out what’s happening. I.E.
they are more timeconsuming than the other questions. However,, looking at the bright side, all the information you need to nail the questions are in the graphs. No more than that. Also, the same notions you have already learned for the other questions  specifically stats and set problems  will help you in this juncture.
Particularly, you have to have
 an eye for details;
 ability to draw the necessary information from the graphs, and avoid those unuseful or irrelevant.
The good news is that the process to nail the question correctly is pretty straightforward.
 When the DI questions, during the exam, pops up in front of you the first thing to do is to have a glance at the image in front of you to see what is going on, for example: if the pie chart expresses values as a percentage, you would expect some sort of question that involves some sort of FDP calculation. As such, you will be prepared on how to approximate, compare fractions, or how to deal with % change!
 Read SUPER carefully the questions. Because often the correct answer depends upon a tiny detail, information, or nuance contained in the graph/table, it is important to figure out what exactly the question wants you to solve.
 Look at the answer choices. If % is involved and the answer choices are far apart, could be the case you might use the estimation strategy;
 If a table with data is involved, find the details for what the question is asking.
In ALL the scenarios above, 99.9999 % of the time, the question involves the following concepts to solve In a nutshell, these types of questions on the GRE are meant to analyze data. To accomplish this effectively and efficiently, you need to know how to make sense of data presented in different types of graphs.
1) The pie or circle chartEach pie chart represents 100 percent of the whole and portions of the pie represent part of the circle. Usually, the pie shows percentages but also amounts. However, in both cases, they are still parts of the whole. Actually, we do have a ratio. A pie chart might show one series of data but also two series of data; in this latter case, certainly, the question will ask you some sort of comparison between the two series or relationships.
Here is an example
You can also have a combination (possible) of a pie chart with data in tables. Tables display data in rows and columns. However, a table is different from a graph, which is a drawing that visually shows the relationship between the data and how the data changes.
We have also examples of three pieces of data represented: tables, pie, and Single Series Column Charts
2) The line graphA line graph consists of two or three axes with data points connected by a line, sort of like a connectthedots exercise. They basically show a trend over the days, months, years or among some kind of quantities. We might have

Two axes: A typical line graph consists of an x (horizontal) and y (vertical) axis, each of which represents a different unit of measure.

Three axes: A graph with three axes contains a second yaxis on the right.
TIPS: Try visual estimation before performing calculations.
3) The column or bar chartA bar graph has vertical or horizontal bars that may represent actual numbers or percentages. Although they look significantly different from line graphs, they’re very similar.
We might have three forms or representations of the bar chart
(
a)  Single Series Column Charts
(
b)  Stacked Column Charts
Also, in this case, the GRE uses them to show two or more data series at a time, as differently shaded parts of one column.
(
c)  Clustered Column Charts
We could have also a combination of line + bar chart
or pie, bar, and table chart
4) The scatter plotA scatter plot is useful for spotting trends and making predictions. It’s similar to a line graph in that it uses horizontal and vertical axes to display the values of the plotted points. With a scatter plot, however, instead of connecting the individual dots, you draw a line to show the flow of data and predict where the future data points are likely to fall. This line is called a trend line or regression line. Sometimes the trend line is drawn, and other times you estimate where it is based on the data flow.
As far as we do know, there is ONE only example of a question with a scatter plot in the entire ETS Official Material ever released by ETS, though!
Keep in mind the following key point to solve always a scatter plot question:
Trend line or regression line: The line passes as closely as possible through the middle of the scattered points.
Correlation: Correlation specifies the direction of the regression line and how closely the two variables correspond:
• Positive correlation: The regression line has a positive slope; that is, the line rises from left to right.
• Negative correlation: The regression line has a negative slope; that is, the line runs downhill from left to right.
• No correlation: If the points are simply scattered all over the graph so that a regression line can’t clearly be determined, the variables have no correlation to one another.
• Strong or weak correlation: The closer the points are to the regression line, the stronger the correlation. Conversely, the farther they are from the line, the weaker the correlation
5) The BoxandWhisker Plots1. A boxandwhisker plot uses a number line to represent the data visually. I.E. It shows visually the
GRE  Mean, Median, Mode, and Range2. It displays a data set along a number line using medians. Quartiles divide the data set into four equal parts. The median (second quartile) divides the data set into two halves. The median of the lower half is the first quartile. The median of the upper half is the third quartile.
3. The box plot does not show
individual data but it analyzes the
spread of data. A measure of spread is a single number that describes how to spread out or clustered together the data are.
4. Another measure of spread is the interquartile range (IQR). The “Interquartile Range” is the difference between the smallest value and the largest value of the middle 50% of a set of data.
The above is an excerpt from my guide that I advise you to read to understand what they are fully
GRE  BoxandWhisker Plots As far as we do know, there is ONE only example of a question with a scatter plot in the entire ETS Official Material ever released by ETS, though!
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