From GMAT Club:
E is a collection of four ODD integers and the greatest difference between any two integers in E is 4. The standard deviation of E must be one of how many numbers?
(A) 3
(B) 4
(C) 5
(D) 6
(E) 7
Answer b
My question:
The way I solved this question was choosing two random odd integers in which the range is 4. I used 1 and 5:
1.) 1115
2.) 1335
3.) 1135
4.) 1315
5.) 1355
6.) 1155
7.) 1555
I then found the average of each set and calculated how far apart each individual number is from the mean of each set:
1.) 1,1,1,3
2.) 2,0,0,2
3.) 1.5, 1.5, .5, 2.5
4.) 1.5, .5, 1.5, 2.5
5.) 2.5, .5, 1.5, 1.5
6.) 2,2,2,2
7.) 3,111
Set 1 and set 7; set 3, set 4, and set 5, all have exactly the same absolute differences in mean. Set 1 and set 7, set 3 and set 5 are also reflexive of each other. Despite the fact that set 4 is not reflexive from set 3 and set 5, it still has the same standard deviation as set 3 and set 5 right?
(Set 4 wasn't explained as part of the solution in the original post on GMAT Club. For more information you can go to https://gmatclub.com/forum/hard-standard ... 99774.html)
E is a collection of four ODD integers and the greatest difference between any two integers in E is 4. The standard deviation of E must be one of how many numbers?
(A) 3
(B) 4
(C) 5
(D) 6
(E) 7
Answer b
My question:
The way I solved this question was choosing two random odd integers in which the range is 4. I used 1 and 5:
1.) 1115
2.) 1335
3.) 1135
4.) 1315
5.) 1355
6.) 1155
7.) 1555
I then found the average of each set and calculated how far apart each individual number is from the mean of each set:
1.) 1,1,1,3
2.) 2,0,0,2
3.) 1.5, 1.5, .5, 2.5
4.) 1.5, .5, 1.5, 2.5
5.) 2.5, .5, 1.5, 1.5
6.) 2,2,2,2
7.) 3,111
Set 1 and set 7; set 3, set 4, and set 5, all have exactly the same absolute differences in mean. Set 1 and set 7, set 3 and set 5 are also reflexive of each other. Despite the fact that set 4 is not reflexive from set 3 and set 5, it still has the same standard deviation as set 3 and set 5 right?
(Set 4 wasn't explained as part of the solution in the original post on GMAT Club. For more information you can go to https://gmatclub.com/forum/hard-standard ... 99774.html)
