standard deviation and the increment detail

[maria08]

An English class has a total of 100 scores whose mean is 72.5 and standard deviation is 4.7. If to each score an additional 5 point increment is added, what is greater.

Column A
Standard deviation of the adjusted 100 scores.

Column B
5.2

Just to double check here - it seems column B is greater as SD does not change post-increment. Is this correct?

[tommywallach]

Absolutely right Maria. The only things that affect Standard Deviation are range (the primary thing) and the number of terms (two terms that differ by 10 have a larger SD than 100 terms interspersed around a range of 10). In this case, neither the # of terms nor the range is changing.

Well done!

-t