The Length of Students' College Careers at Anytown University Is

Multiple Choice

The length of students' college careers at Anytown University is known to be Normally distributed, with a mean length of 5.5 years and a standard deviation of 1.75 years. If a sample of size 20 is repeatedly chosen at random, what is the standard deviation _x of sample means?

A) 5.5 years
B) 1.75 years
C) 1.23 years
D) 0.39 years