Standard deviation of the sample mean from an infinite population

[Amy-Lee]

Homework Statement

Consider an infinite population with the mean of 160 and a standard deviation of 25. A random size 64 is taken from this population.
What does the standard deviation of the sample mean equal to?

Homework Equations

How do I answer this question without a given population size or proportion of the population?

The Attempt at a Solution

 

[Mark44]

Look in your textbook for the distribution of sample means. It might also be under standard error of the mean.