1. Chebyshev inequality

Hi all,
I would appreciate if someone could help me with this question.

How I can ,using Chebyshev inequality, prove that a least $\displaystyle${15}/{16} of all bitstrings $\displaystyle$x \in \{0,1\}^n of length n have hamming weight that could satisfy the following relation $\displaystyle$ {n}/{2} - {4 \sqrt{n}}/{2} \leq wt(x) \leq {n}/{2} + {4 \sqrt{n}}/{2}. wt(x) is hamming wieght.