GRE Topics - standard deviation?

[Armymutt25A]

It's been a while since I took the GRE, but I don't recall std deviations being on it. Did anyone encounter it on a recent exam? I thought the test focused on basic high school level math with a few tricks here and there. I'm pretty sure I didn't do anything with std deviations in high school. Seems like it would take a while to do one question.

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[Minnerbelle]

It's been a while since I took the GRE, but I don't recall std deviations being on it. Did anyone encounter it on a recent exam? I thought the test focused on basic high school level math with a few tricks here and there. I'm pretty sure I didn't do anything with std deviations in high school. Seems like it would take a while to do one question.

i did a google search, and it says that they've been popping up recently so it's good to know. it won't take long to do if they only have a data set of n<5. oh, but it looks like they generally don't ask you to calculate the SD point blank though.

according to spark notes:

"Standard deviation is one of the most difficult statistical concepts, but thankfully you'll only need a very general understanding of it for the GRE. The test makers won't ask you to actually calculate standard deviation, as the formula for doing so is pretty difficult. You will, however, be expected to know that standard deviation is a measure of how spread out a group of numbers is. The more spread out a group of numbers, the larger its standard deviation. Let's look at an example: Which of the following groups of numbers has the greater standard deviation?
Group A: 11, 12, 13, 14, 15
Group B: 50, 51, 51, 52, 53
Even though the numbers in Group B are larger than those in Group A, they're closer together thanks to the double occurrence of number 51. No such overlapping occurs in Group A. Group A exhibits a slightly greater spread and therefore has the greater standard deviation."


(fyi - i'm positive we covered stdev in my algebra ii/trig class back in the day.)

 

[BlacKAT33]

i did a google search, and it says that they've been popping up recently so it's good to know. it won't take long to do if they only have a data set of n<5. oh, but it looks like they generally don't ask you to calculate the SD point blank though.

according to spark notes:

"Standard deviation is one of the most difficult statistical concepts, but thankfully you’ll only need a very general understanding of it for the GRE. The test makers won’t ask you to actually calculate standard deviation, as the formula for doing so is pretty difficult. You will, however, be expected to know that standard deviation is a measure of how spread out a group of numbers is. The more spread out a group of numbers, the larger its standard deviation. Let’s look at an example: Which of the following groups of numbers has the greater standard deviation?
Group A: 11, 12, 13, 14, 15
Group B: 50, 51, 51, 52, 53
Even though the numbers in Group B are larger than those in Group A, they’re closer together thanks to the double occurrence of number 51. No such overlapping occurs in Group A. Group A exhibits a slightly greater spread and therefore has the greater standard deviation."


(fyi - i'm positive we covered stdev in my algebra ii/trig class back in the day.)

this is exactly what i was going to say. and nice example! in the GRE review books they will tell you this. You dont need to calculate the exact thing but you need to be able to look at a set of numbers and know which has a bigger/small stdev

 

[turquoisewolves]

Okay, I'm awful at explaining things sometimes, so bear with me
But on one of the questions that I got last week, I had to know the percentiles of the bell curve (34%, 14%, 2%) and then work out a problem (it wasn't just the comparison part).

it was kind of like one of my practice questions from Princeton Review:

The fourth grade at School X is made up of 300 students who have a total weight of 21,600 pounds. If the weight of these fourth graders has a normal distribution and the standard deviation equals 12 pounds, approximately how many of the fourth graders weigh more than 84 pounds?

So you just have to plot everything out on the bell curve.
average weight is 72 pounds
12 pound STD

2%---48lbs---14%--60lbs---34%--72lbs--34%--84lbs--14%--92lbs--2%
So you if you are in the 4th grade and weigh MORE than 84 pounds that equals (14%=2%=16%) which is 48 kids

Hope this helps....a little, lol

 

[Armymutt25A]

Hope this helps....a little, lol

That helps - brings to light something that I don't recall covering in my trig or alg II class in '93. I haven't seen a question like that on any of the practice materials I have.

 

[nyanko]

Basic statistical concepts being covered gets a huge from me, since IMO that's a far more important thing to understand for grad school and for day to day life than most of the other topics covered on the GRE quant.

You can't interpret a study in any field if you don't understand what things like standard deviation, standard error, percentiles, confidence intervals, measures of central tendency and such actually mean!

I don't remember if those things were on the GRE when I took it or not, because I would have easily gotten them. However, I'm pretty sure I do remember them being on the ACT when I took it back in the dark ages.

edit: It's very plainly stated here under "Data Analysis" that descriptive statistics and elementary probability are part of the quant section...

 

[ATX00]

The fourth grade at School X is made up of 300 students who have a total weight of 21,600 pounds. If the weight of these fourth graders has a normal distribution and the standard deviation equals 12 pounds, approximately how many of the fourth graders weigh more than 84 pounds?

So you just have to plot everything out on the bell curve.
average weight is 72 pounds
12 pound STD

2%---48lbs---14%--60lbs---34%--72lbs--34%--84lbs--14%--92lbs--2%
So you if you are in the 4th grade and weigh MORE than 84 pounds that equals (14%=2%=16%) which is 48 kids

Hope this helps....a little, lol

There was one standard deviation question on the GRE when I took it recently, and it was set up almost exactly like this example.

 

[that redhead]

To be honest, I haven't heard that SD will be on the GRE. All of the practice questions I've done haven't had anything to do with SD, so I'll be in for a surprise if they pop up on mine on Saturday scared

 

[Jakesmom]

I took the GRE in January and had 2 fun-filled quantitative sections and did not have a single problem asking about st. dev.

 

[squibby]

I got one last summer that basically asked me how many st. deviations away from the average a number was, given the standard deviation. Super easy.

 

[rileydog]

To be honest, I haven't heard that SD will be on the GRE. All of the practice questions I've done haven't had anything to do with SD, so I'll be in for a surprise if they pop up on mine on Saturday scared

I don't remember if there was a standard deviation problem on my GRE or not. If you are worried about it, I would just know basically what it means. The sample given by Minnerbelle is probably all you need to know. And if it is on there, it would probably only be one question. If you miss one question, it is not the end of the world. For me, there are some math problems/concepts that I have a mental block about. No matter how much I study how to do it, I just can't solve it. For me, it is not worth spending a ton of time trying to figure out the ones I have trouble with. I would rather try to make a good guess and move on so that I can complete the ones I can solve in the time left. Obviously if you are guessing on every one, thats a problem, but I don't think you need to know everything perfectly to get a competitive score.

 

[GreennWhite]

One of the last questions on my portion of the quantitative section was a std dev question - that's how I knew I was doing so well! So if you get one - you're probably doing well!

 

[Armymutt25A]

I've done 2 tests in the past two days. So far, I keep screwing up simple things - like thinking 15 is a prime number and such. There have been 1 or 2 that either stumped me, or, in the case of graph interpretation, I'm just not pulling the same data from the charts. There's a few concepts I need to brush up on - never really had geometry as a separate subject. While one question is just one question, it's a 10pt difference.