Source: Official Guide Revised GRE 1st Ed. Part 6; Set 3; #2

10

In the course of an experiment, 95 measurements

In the course of an experiment, 95 measurements were recorded, and all of the measurements were integers. The 95 measurements were then grouped into 7 measurement intervals. The graph above shows the frequency distribution of the 95 measurements by measurement interval. Quantity A : The average (arithmetic mean) of the 95 measurements Quantity B : The median of the 95 measurements Quantity A is greater., Quantity B is greater., The two quantities are equal., The relationship cannot be determined from the information given.

3 Explanations

1

vaishali shetty

what does skewed to the left mean? if it is going towards left doesnt it mean th value is 1-5 which is lesser than 6-10?

Jul 11, 2016 • Comment

Cydney Seigerman, Magoosh Tutor

Hi Vaishali :)

"Skewed to the left" means that the long "tail" of the graph is on the left hand side. This is also called a negative skew, as the long tail is on the negative side of the peak.

In the practice problem, the tail is to the right of the peak, which is why we consider the graph skewed to the right.

Hope that helps!

Jul 11, 2016 • Reply

2

CHAHAT RUSTAGI

I am really not clear with the MEAN part! Please re-explain.

Jan 19, 2016 • Comment

Cydney Seigerman, Magoosh Tutor

The mean is the average value of a set of numbers. If we have a symmetrical distribution, the average will be close to the median, or middle number, of that distribution. This is what Chris shows when he discusses what is observed in intervals 1-5, 6-10, and 11-15. Because there are 15 measurements in the 1-5 interval and 15 measurements in the 11-15 interval, if we were to ignore the measurements above the 11-15 interval, we could conclude (without doing any calculations) that the mean will be in the 6-10 interval and very close to the median. The mean could be slightly higher or lower or the same as the median, depending on the exact values within the 6-10 interval.

However, in this problem, because there are values above the 11-15 range, we can determine that the average will be skewed to the left, making the average greater than the median.

I hope this helps! :)

And for more review on mean, median, and mode, check out the following post from our GRE blog :D

http://magoosh.com/gre/2014/mean-median-and-mode-on-the-gre/

Jan 21, 2016 • Reply

7

Gravatar Chris Lele, Magoosh Tutor

Oct 7, 2012 • Comment

jishu kumar dey

i think the graph represents a positively skewed shape and since 1st 3 bar mean is clearly 6-10 .but the presence of some extreme values i mean the last part make the mean greater than 6-10.am i right ?

Jun 19, 2016 • Reply

Cydney Seigerman, Magoosh Tutor

Hi Jishu :)

Yes, you're correct that we have a positively skewed distribution. Since we have values greater than 11-15, we can conclude that the average will be greater than the median :)

Jun 21, 2016 • Reply

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