A set of data consists of the following 5 numbers: 0,2,4,6, and 8. Which two numbers, if added to create a set of 7 numbers, will result in a new standard deviation that is close to the standard deviation for the original 5 numbers?

Question

anonymous · Answer

SD now is sqrt 40/4 so u want to add 2 numbers (say sum x) which will increase the SD to  sqrt((40 +x)/6) and still have that equal sqrt 10.

This gives x as 20 but u do not want the numbers to be outside the range of the existing data set because that will tend to increase the SD so that suggests adding a pair of 8's producing an SD of 3,23 versus 3.16.

You did not specify integers, if it is not integers there might be a better answer, this is just quick and dirty, is it close enough?

anonymous · Answer

Actually, a pair of 0's will work equivalently.