Thread: Standard deviation help please

I am sorry that I am asking this question as I'm sure that this is very simple for people on this site but I'm a Masters student who has not taken Linear equations before and have questions and am having a hard time with a problem, here it is:

A study was conducted involving 20 young children. the mean age of the children was 4.0 years, and the standard deviation was 1.2 years. A colleague recommends that age be reported in months rather than years. What is the standard deviation when the childrens age is expressed in months rather than years?

Originally Posted by quetadave

I am sorry that I am asking this question as I'm sure that this is very simple for people on this site but I'm a Masters student who has not taken Linear equations before and have questions and am having a hard time with a problem, here it is:

A study was conducted involving 20 young children. the mean age of the children was 4.0 years, and the standard deviation was 1.2 years. A colleague recommends that age be reported in months rather than years. What is the standard deviation when the childrens age is expressed in months rather than years?

Let Y = aX + b.

Then E(Y) = a E(X) + b, Var(Y) = a^2 Var(X) and sd(Y) = |a| sd(X).

Your job is to get a relationship between X (age measured in years) and Y (age measured in months) and then get sd(Y).