If d is the standard deviation x, y, and z, what is the standard deviation of 2x, 2y, 2z ?
Options:
A) d
B) 2d
C) 15d
D) d + 5
E) d + 15
If we add or subtract a constant to each term in a set:   Mean will increase or decrease by the same constant.   SD will not change.   If we increase or decrease each term in a set by the same percent (multiply by a constant):   Mean will increase or decrease by the same percent.   SD will increase or decrease by the same percent.   So in our case SD will change by same multiple (% increase) as we are multiplying each number in a set by 2--&gt; SD=2d.   Answer: 2d.
<result>B</result>
If d is the standard deviation x, y, and z, what is the standard deviation of 2x, 2y, 2z ?