Question

GRE Tutorial: Data Interpretation Tips

Answer 1

\({\bf{What~is~Data~Interpretation?:}}\) Data interpretation is a particular type of question on the GRE math section. Out of 40 math questions you should expect to see about 6 of these types of questions. You will be given data in the form of graphs, tables, or charts, and asked questions based on the data. The calculations will typically be very simple, such as finding quantities, rates of change, or proportions among the categories in the data.

\({\bf{How~to~Approach~the~Problems:}}\) It may be overwhelming at first, to see such large amounts of data being presented at once. That being said, you should first identify what type of graph, table, or chart is being presented (pie chart, bar graph, line graph, two-way table, etc.). Then, look at any titles and axes given, making sure to be careful about what units are specified.

I will use an example from the ETS website

https://www.ets.org/gre/revised_general/prepare/quantitative_reasoning/data_interpretation/sample_questions

At first, we notice that it is a table with the title "Annual Percent Change in Dollar Amount of Sales at Five Retail Stores from 2006 to 2008"

The left column specifies five retail stores, P to T, and the units in the table are percentages. We are not given the actual dollar amounts, just the percentages. A positive percent change indicates that the store made more money than the previous year, while a negative percent change indicates that the store made less money than the previous year.

Answer 2

Let's go through the three sample problems one by one:

If the dollar amount of sales at Store P was $800,000 for 2006, what was the dollar amount of sales at that store for 2008?

Here's where we have to be very careful about the units in the table. a 10% increase and a 10% decrease do NOT cancel each other out. They must be calculated separately.

10% increase ---> 1.1 * 800,000
10% decrease ---> 1.1 * 0.9 * 800000

Answer 3

Problem 2:

At Store T, the dollar amount of sales for 2007 was what percent of the dollar amount of sales for 2008? Give your answer to the nearest 0.1 percent.

we don't know exactly how much store T made in 2007 (or any year for that matter) so we can use a generic variable T to represent sales in 2007.

sales in 2007 = T
sales in 2008 = 0.92*T (remember, this is an 8% decrease)

so 100* (sales in 2007) / (sales in 2008) = 1/0.92 = about 108.7%

two things to be wary of: the units (nearest 0.1 percent) AND the exact phrasing of the percent calculation. it wants the percentage of the 2007's sales out of the 2008's sales, so the 2007 sales need to be in the numerator and the 2008 sales need to be in the denominator. If we do it the other way around we will get the wrong answer.

Answer 4

Problem 3: Based on the information given, which of the following statements must be true?

Indicate all such statements.

1. For 2008 the dollar amount of sales at Store R was greater than that at each of the other four stores.
2. The dollar amount of sales at Store S for 2008 was 22 percent less than that for 2006.
3. The dollar amount of sales at Store R for 2008 was more than 17 percent greater than that for 2006.

Again, since we aren't given dollar amounts we cannot verify statement 1, so we exclude that from our possible choices. At this point there are only three possibilities (statement 2 is correct, statement 3 is correct, or both statements are correct). Eliminating a choice greatly improves your probability of guessing correctly if you can't figure out the rest.

for statement 2, we can try to plug in something for the dollar sales in 2006.

if sales in 2006 = 100
then sales in 2007 = 93 (a 7 percent decrease)
and sales in 2008 must therefore be (0.85)(93) = 79.05 which is a 20.95% decrease not a 22% decrease. so statement 2 is off as well.

at this point it's gotta be statement 3 but let's be doubly sure.

it's a 5 percent increase AND a 12% increase so that ends up as

1.05 * 1.12 * original sales which is 1.176 times the original sales, so yes, this is more than a 17% increase

Answer 5

\({\bf{General~Advice:}}\)

1. Read the problem very carefully and answer the question that is being asked. This is good practice in general, but especially important for these questions, when word choice and word order make a huge difference in the outcome. Also consider whether the question is asking for something that is not possible to answer with the given data. For example, if a graph only gives percentage changes and not raw numbers, you will not be able to give a raw number unless they give you a raw number first.

2. Be very careful with units. often times, the units may be in hundreds, thousands, millions, etc. they might even give you two graphs that have similar data but different units, so you have to convert them to the same unit if you want to compare between them.

3. Practice estimation. often times the data value will not lie neatly on a tick mark so you have to estimate where it would be. usually the answer choices are spaced out enough to give you some wiggle room when it comes to estimation.

4. Use your calculator wisely. it's easy to miss a zero especially when working with very large numbers. you might not always need to punch in the whole number anyway; for example, if they ask you to calculate a 17% decrease from 20.5 million in sales, you just need to calculate 83% of 20.5, or 0.83 * 20.5 rather than deal with all those zeros.

5. As usual, check to make sure your answer is reasonable. Ex: If the question asks for a percent decrease, your final answer should be smaller than the original quantity.

Answer 6

Anyway, that's the end of my tutorial, I hope it was a helpful resource. Source material is the ETS Data Interpretation Sample Questions website and the 19th edition Barron's prep book for the new GRE.