Author 
Message 
TAGS:


GRE Prep Club Legend
Joined: 07 Jun 2014
Posts: 4856
WE: Business Development (Energy and Utilities)
Followers: 102
Kudos [?]:
1734
[3]
, given: 397

The standard deviation of the set 1, 5, 7, 19 [#permalink]
03 Jul 2016, 16:03
3
This post received KUDOS
Question Stats:
76% (00:24) correct
23% (00:18) wrong based on 21 sessions
Quantity A 
Quantity B 
The standard deviation of the set 1, 5, 7, 19 
The standard deviation of the set 0, 5, 7, 20 
A)The quantity in Column A is greater. B)The quantity in Column B is greater. C)The two quantities are equal. D)The relationship cannot be determined from the information given.
_________________
Sandy If you found this post useful, please let me know by pressing the Kudos Button
Try our free Online GRE Test




Manager
Joined: 23 Jan 2016
Posts: 137
Followers: 3
Kudos [?]:
110
[2]
, given: 15

Re: The standard deviation of the set 1, 5, 7, 19 [#permalink]
04 Jul 2016, 21:05
2
This post received KUDOS
Both sets have same mean, but second set has more dispersion from the mean, hence SD of the second set will be more. hence B



Director
Joined: 03 Sep 2017
Posts: 521
Followers: 1
Kudos [?]:
343
[1]
, given: 66

Re: The standard deviation of the set 1, 5, 7, 19 [#permalink]
01 Oct 2017, 06:14
1
This post received KUDOS
Just to be a little more formal I provide my solution.
Since the two groups have the same mean (= 10), we can get rid of the common numbers on the two lists, i.e. 5 and 7, since they would provide the same difference from the mean for the two columns. Then, we are left with 1 and 19 on column A and 0 and 20 on column B.
Instead of using the real standard deviation formula, we can get an idea using an approximate formula that is computed as the mean of the differences of the numbers from the mean. Thus, in column A we get 9+9/2 = 9 and on column B, 10+10/2 = 10. Thus, the standard deviation is higher in column B.
Answer B!



Director
Joined: 20 Apr 2016
Posts: 809
WE: Engineering (Energy and Utilities)
Followers: 9
Kudos [?]:
582
[0], given: 113

Re: The standard deviation of the set 1, 5, 7, 19 [#permalink]
01 Oct 2017, 07:36
IlCreatore wrote: Just to be a little more formal I provide my solution.
Since the two groups have the same mean (= 10), we can get rid of the common numbers on the two lists, i.e. 5 and 7, since they would provide the same difference from the mean for the two columns. Then, we are left with 1 and 19 on column A and 0 and 20 on column B.
Instead of using the real standard deviation formula, we can get an idea using an approximate formula that is computed as the mean of the differences of the numbers from the mean. Thus, in column A we get 9+9/2 = 9 and on column B, 10+10/2 = 10. Thus, the standard deviation is higher in column B.
Answer B! COuld you plz explain, i failed to understand 1. how you got the mean of setA = mean of set B = 10? 2. 9+9/2 = 9? how we get?
_________________
If you found this post useful, please let me know by pressing the Kudos Button
Rules for Posting https://greprepclub.com/forum/rulesfor ... 1083.html



Director
Joined: 03 Sep 2017
Posts: 521
Followers: 1
Kudos [?]:
343
[0], given: 66

Re: The standard deviation of the set 1, 5, 7, 19 [#permalink]
01 Oct 2017, 07:47
pranab01 wrote: IlCreatore wrote: Just to be a little more formal I provide my solution.
Since the two groups have the same mean (= 10), we can get rid of the common numbers on the two lists, i.e. 5 and 7, since they would provide the same difference from the mean for the two columns. Then, we are left with 1 and 19 on column A and 0 and 20 on column B.
Instead of using the real standard deviation formula, we can get an idea using an approximate formula that is computed as the mean of the differences of the numbers from the mean. Thus, in column A we get 9+9/2 = 9 and on column B, 10+10/2 = 10. Thus, the standard deviation is higher in column B.
Answer B! COuld you plz explain, i failed to understand 1. how you got the mean of setA = mean of set B = 10? 2. 9+9/2 = 9? how we get? The results are that because I got rid of the numbers who are equal in the two columns, i.e. 5 and 7. In that way we get that the mean is 1+19/2 = 10 and 0+20/2 = 10. Than the sd are (101)+(1910)/2 = 9 and (100)(2010)/2 = 10. This is kind of an approximation that is faster to compute. However, you could have worked with the two full list as well. Getting the same mean of 8 for the two lists and sd = 5.5. for quantity A and sd = 6 for quantity B. Leading to the same answer, B!



Director
Joined: 20 Apr 2016
Posts: 809
WE: Engineering (Energy and Utilities)
Followers: 9
Kudos [?]:
582
[0], given: 113

Re: The standard deviation of the set 1, 5, 7, 19 [#permalink]
01 Oct 2017, 08:59
IlCreatore wrote: pranab01 wrote: IlCreatore wrote: Just to be a little more formal I provide my solution.
Since the two groups have the same mean (= 10), we can get rid of the common numbers on the two lists, i.e. 5 and 7, since they would provide the same difference from the mean for the two columns. Then, we are left with 1 and 19 on column A and 0 and 20 on column B.
Instead of using the real standard deviation formula, we can get an idea using an approximate formula that is computed as the mean of the differences of the numbers from the mean. Thus, in column A we get 9+9/2 = 9 and on column B, 10+10/2 = 10. Thus, the standard deviation is higher in column B.
Answer B! COuld you plz explain, i failed to understand 1. how you got the mean of setA = mean of set B = 10? 2. 9+9/2 = 9? how we get? The results are that because I got rid of the numbers who are equal in the two columns, i.e. 5 and 7. In that way we get that the mean is 1+19/2 = 10 and 0+20/2 = 10. Than the sd are (101)+(1910)/2 = 9 and (100)(2010)/2 = 10. This is kind of an approximation that is faster to compute. However, you could have worked with the two full list as well. Getting the same mean of 8 for the two lists and sd = 5.5. for quantity A and sd = 6 for quantity B. Leading to the same answer, B! From where have you got the formula for SD : Im not sure of that formula Secondly if we look at both qty's we can see that the smaller number in qty B < qty A and bigger number in qty B> qty A. So definitely QTY B is more spread out than QTY A. and so the option is B
_________________
If you found this post useful, please let me know by pressing the Kudos Button
Rules for Posting https://greprepclub.com/forum/rulesfor ... 1083.html




Re: The standard deviation of the set 1, 5, 7, 19
[#permalink]
01 Oct 2017, 08:59





