Calculate population cumulative probability from sample

Hi all,
I am currently working on an assignment that involves inferential statistics. Basically, I am given a sample of 30 people with their heights and I am asked to calculate the confidence interval of the population and the population cumulative probability of people who have heights over 1.8m(the population proportion for people that are taller than 1.8m). The first part is easy. How should I solve the second part of the question? Should I use Z-score or T-score?

Thank you very much!
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