Heights of male students.

To estimate the mean height of u (population mean) of male students on your campus, you will measure an SRS of students. You know from the government data that the standard deviation of the heights of young men is about 2.8 inches. How large an SRS must you take to reduce the standard deviation of the sample mean to one-half inch?

I did this.....

Solve: 2.8/sqrt(n)=1.5

2.8=1.5xsqrt(n)

sqrt(n)=2.8/1.5

(sqrt(n))^2=(1.866)^2

n=3.484

I really don't think that this is right!!!!