Post your question in the Comment section below, and a GRE expert will answer it as fast as humanly possible.
- Video Course
- Video Course Overview
- General GRE Info and Strategies - 7 videos (free)
- Quantitative Comparison - 7 videos (free)
- Arithmetic - 42 videos
- Powers and Roots - 43 videos
- Algebra and Equation Solving - 78 videos
- Word Problems - 54 videos
- Geometry - 48 videos
- Integer Properties - 34 videos
- Statistics - 28 videos
- Counting - 27 videos
- Probability - 25 videos
- Data Interpretation - 24 videos
- Analytical Writing - 9 videos (free)
- Sentence Equivalence - 39 videos (free)
- Text Completion - 51 videos
- Reading Comprehension - 16 videos
- Study Guide
- Philosophy
- Office Hours
- Extras
- Prices
Comment on Units of Standard Deviation
When the question asks for
The question is asking us to
The question is asking us to identify all values that are more than 0.5 units of standard deviation BELOW the mean.
0.5 units of standard deviation BELOW the mean = 9 - (0.5)(4.2) = 6.9
0.6 units of standard deviation BELOW the mean = 9 - (0.6)(4.2) = 6.48. This means that 6.48 is more than 0.5 units of standard deviation BELOW the mean
Likewise, 0.7 units of standard deviation BELOW the mean = 9 - (0.7)(4.2) = 6.06. This means that 6.06 is more than 0.5 units of standard deviation BELOW the mean
Does that help?
So, What happen with numbers
The question does not ask us
The question does not ask us to identify values that are more than 0.5 units of SD AWAY from the mean. It asks us to identify values that are more than 0.5 units of SD BELOW (less than) the mean
Thanks so much. Probability,
im really amazed with ur
Glad to help!
Glad to help!
Hi! Can you use a proportion
Most definitely!
Most definitely!
Great exercise!. At first I
how do you determine 6 as the
7.6 below , 12, mean 16.4 above.
Tuttiam52 isn't saying that
Tuttiam52 isn't saying that the correct answer is 6.
With "Units of Standard Deviation (SD)" questions, we often look at units of SD ABOVE the mean and units of SD BELOW the mean.
This question asks for 0.5 units of SD BELOW the mean.
So, we must SUBTRACT 2.1 from the 9 (the mean)
For more on this see: https://www.greenlighttestprep.com/module/gre-statistics/video/808
Thank you so much for the
Thanks for the kind words,
Thanks for the kind words, Reetika!
Hi Brent,
Thank you very much for this explanation!
I have a question, if they would ask us to find all values that are 0.5 standard deviation below the mean, meaning between 6.9 and 9.
The values are like this: 7,7,7,8,8,8
Should we include 9 as well or not? Thanks
If the question asked "find
If the question asked "find all values that are 0.5 standard deviations BELOW the mean", then the ONLY value that satisfies that condition is 6.9, since 6.9 is 0.5 standard deviations below the mean.
If the question asked "find all values that are LESS THAN 0.5 standard deviations BELOW the mean", then the values that satisfy that condition are 7,7,7,8,8,and 9.
9 work because 9 is 0 standard deviations below the mean.
Cheers,
Brent
Thanks Brent now it is clear!
It is an interesting usage of
Good question.
Good question.
Here's an example from the official GRE Guide:
Example 4.2.9: Six hundred applicants for several post office jobs were rated on a scale from 1 to 50 points. The ratings had a mean of 32.5 points and a standard deviation of 7.1 points. How many standard deviations above or below the mean is a rating of 48 points? A rating of 30 points? A rating of 20 points?