In the fall of 2000, 54% of the almost 34,000 first-year students attending one of the California State Universities had strong enough math skills to take an entry level course.

1)Based on a sample of 20 students, can we assume our calculations will be accurate?
My answer is: yes, I got .5398. Can someone double check me.

2) What value will we use for the standard deviation for a sample of 100 students:
My answer: 4.98

Any help would be appreciated.
Thanks