# استراتژی تفسیر داده

سرفصل: بخش ریاضی / سرفصل: تفسیر داده / درس 2

## بخش ریاضی

14 سرفصل | 192 درس

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## Data Interpretation Strategy

Now, we can talk about some data interpretation strategies, and the first thing I’ll say is, why do you think human beings came up with the idea of graphs? Why do we display mathematical information in graphs? Why is it, for example, when you flip through the Wall Street Journa,l or The Economist Magazine that inevitably you’re gonna see some graphs? Or if you open up almost any scientific textbook, inevitably there’s gonna be some graphs, and charts.

Why is it that human beings are so prone to do this? Think about it, think about it this way, suppose I gave you a list of 100 numbers. So, a printed list, 100 numbers that could be say monthly readings of some economic indicator for the last 100 months. I gave you this list, and then I said find the lowest value, or find the highest value.

And of course, it would be a cumbersome task. It would take you quite some time to sort through a list of numbers, and find which one was highest, which one was lowest. But if I gave you a graph, suppose I had a graph like this. Well, then right away you could say, oh, well, looks like that’s probably the highest point, that’s a little higher than this, and that’s probably the lowest point, depending on how we count the starting point.

But that, in other words, right away you could pick out a high point and a low point very easily. And this is because the back half of the cerebral cortex, the human cerebral cortex is purely devoted to processing visual information is. Something called the occipital lobe of the brain. It is the worlds best visual processing machine, the best visual processing machine in the entire universe basically.

It’s absolutely incredible what we do when we process visual information. In fact, we do it so seamlessly, so naturally, we tend to take it for granted, but its actually an amazing set of powers that we have. And when you learn to read graphs, you’re really tapping into these fundamental human visual skills. So, now having settled that, we can talk about actual strategy for the data sufficiency.

The big idea is understanding the story of the graph. So there’s several layers here. What do I mean by this? This is something that happens relatively quickly. It happens, say, you know, ten or 15 seconds. You just glance it over, and you get the story of the graph.

So, what’s involved in getting the story? Well, first of all, you might have to read any accompanying text, which may, or may not explain some things that are not clear from the graph itself. It’s always important to look at the axes, and notice any units on the axes. Also notice whether the axes start at zero or some other number, and whether they increase by equally spaced intervals or some other intervals, so all those are things to notice.

But the really big idea is, what’s going on with the data on the graph? What patterns are apparent in the data, and what do they mean? Is there an upward trend, a downward trend? Does the graph start out, or end relatively flat? Are there notable high points, or low points? Is it a repeated pattern?

So, for example, if we look at this first graph here. Well, it’s summing. It starts out low and then goes up. Well, if that’s profits of a company, that would be a great story. Looks like they were chugging along. And all of a sudden, wow.

Their profits really shot up. But if it were crimes in a city, or if it were incidences of a certain disease, this would be a very troubling graph. Oh, my God, look how much it shot up, how many more crimes there are, or how many more cases of this particular disease. So, in other words, the actual scenario tells you whether the graph is something very good, or very bad.

You should have a gut sense, kind of an immediate gut sense, when you look at this. Whether it’s wow, this is really good for the people, or oh, this is really bad, that sort of thing. Similarly, this graph that would be excellent if that were cases of a disease. Very infectious and then I guess they figured out how to cure it because the case has really dropped off.

But if it were the profits of a company, oh, that company is really in trouble. You see there’s a story there. Now, this final one, that’s a repeating pattern. So, that would be exactly what we’d expect, if we were looking at, and say, tides, or daylight, or seasons, or something like that. But if we’re actually looking at the profit of a company, that’s a company who just goes, undergoes seasonal fluctuations, and is never able to get anywhere.

You it could imagine it being very frustrating for a company to have its profits always stuck in a certain range have, to have range-bound profits that’s the way it would be discussed in the business world. So, there’s a profound story to any graph, and that’s what you’re trying to understand, and notice just with a glance, as long as you know the scenario, just a glance tells you a whole lot of information.

You could also analyze, is an increase, or decrease good or bad for anyone? We talked about that a little bit, and does one factor appear to influence another. Well, this is interesting, for example, if we look at the graph on the left. As this variable, whatever that is, increases, this one increases at a slow rate, and at a certain point it just shoots up.

So, that’s very interesting, and it definitely appears that one is influencing the other. This one’s interesting because when we move back, and forth along this variable, there are low values at very, at very low values of this variable, or very high values of this variable we get low output. But there’s kind of a sweet spot in the middle, where you get very high values.

So, that’s a very interesting kind of variable. It’s hard to imagine, but there certainly are scenarios in the world where too much, or too little is not good, but just right is very good. That’s the kind of graph, we have on the, on the right there. Also, check the units in the question.

They may or may not match the data. And GRE love this sort of, switch. For example, giving you dollars per month on the graph, and then dollars per year, or dollars per week, or something like that in the question. So, beware of ways that they might be switching up the units between the graph, and the question.

Check the form of your answer before you, before you do calculations cuz that will also tell you the units, tell you whether you’re dealing with fractions, or percents. And if the answers are spaced wide apart, this indicates that we are free to estimate. Remember our discussion of estimation from the General Math Strategy lessons.

In general, the GRE is not interested in your ability to perform detailed calculation. It is interested in you’re ability to use logic, and reasoning to come to answers quickly, and estimation is a big part of this. Because all the graphs on the GRE Data Interpretation are drawn to scale, that’s a big idea.

All of them are drawn to scale. We are free to use visual estimation. Also I’ll say, don’t confuse numerical differences with percent differences. Now, what do I mean by that? Look at this data here. So, it’s clear from this data that which country, of these two countries, which one had the biggest percent increase from 2000 to 2010.

Well, clearly, Malugia had a 20% increase, and Aplandia only had a 5% increase. So, Malugia had a bigger percentage increase, but of course, the GRE probably is not gonna ask you a question about numbers printed on the page. It would be more likely to ask something like, which one had more people added to the population between 2000 and 2010. All right, well, that’s tricky.

So, Malugia, they added 20%. So, 10% of that number is 30,000, so 20% would be 60,000. There’s 60,000 more people in Malugia. Well, in Aplandia, 10 million, 10% of that would be 1 million, and half of that would be 500,000, half a million. And so, even though Malugia increased by a higher percentage.

Aplandia increased more, when we talked about number of people. So, it’s very important not to confuse numerical differences with percent differences. Very, very different. These are some general strategies. The most important aspects of understanding GRE Data Interpretation involves, understanding the various kinds of graphs.

The next video lessons will review these types of graphics. I’ll also say, practice out in the world. Read newspapers, read magazines, especially economic magazines. Look for graphs, practice looking at graphs, practice trying to understand what story the graph is telling. For example, if it appears in a magazine article, or newspaper article.

What art, what is the story of the article, and how is the story of the graph supporting the story of the article? Why is it part of the article? Those are very important things to practice, especially if you need to work on your graph building skills.

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