Consider X as the  aleatory  variable that count the number of letters in a word. Write a function that, give in input an array of words (strings), calculate the  variance  of X.
Max decimal of the variance : 4.

Some wiki: Variance ,
 Aleatory variable 

Example:

Consider "Hello" and "World":

X is { 5 } with P(X = 5) = 1 beacuse the two words has the same length.  
So E[X] = 5 x 1 = 5 and the standard formula for variance is E[(X - u)^2] so  1 x (5-5)^2 = 0
or you can calculate with the other formula E[X^2] - E[X]^2 = 5^2 x 1 - 5^2 = 0

Consider "Hi" and "World":

X is { 2, 5 } with P(X = 5) = 1/2 and P(X = 2) = 1/2.  
So E[X] = 5 x 1/2 + 2 x 1/2 = 3.5 and the standard formula for variance is E[(X - u)^2] so  1/2 x (2-3.5)^2 + 1/2 x (5 - 3.5)^2 = 2.25
or you can calculate with the other formula E[X^2] - E[X]^2 = (5^2 x 1/2 + 2^2 x 1/2) - 3.5^2 = 2.25

```python

USER_FILENAME = "<user_code>"
import sys, json, builtins
import math, heapq, bisect, itertools, functools, collections, statistics, fractions, decimal, operator, array, random, re, string, os, pathlib
try:
    import resource as _res
except Exception:
    _res = None
from collections import Counter, defaultdict, deque, OrderedDict
from functools import lru_cache, reduce
from itertools import accumulate, permutations, combinations, product
from math import gcd, ceil, floor, sqrt
from decimal import Decimal
try:
    from typing import *
except Exception:
    pass
try:
    sys.setrecursionlimit(1_000_000)
except Exception:
    pass
try:
    import site as _site
    try:
        _sys_sites = _site.getsitepackages() if hasattr(_site, "getsitepackages") else []
        for _p in _sys_sites:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
    try:
        _usp = _site.getusersitepackages()
        if isinstance(_usp, str):
            _usp = [_usp]
        for _p in _usp:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
except Exception:
    pass

def _disabled_input(*args, **kwargs):
    raise RuntimeError("input() is disabled in callable mode")
builtins.input = _disabled_input

ns = {"__name__": "__judge__"}  # prevent if __name__ == "__main__" blocks
for _k, _v in list(globals().items()):
    if not _k.startswith("_"):
        ns[_k] = _v
_CODE = 'def variance(li):\n    common = 1 / len(li)\n    e_of_x = sum(len(i) * common for i in li)\n    result = sum((len(i) ** 2) * common for i in li) - e_of_x ** 2\n    return round(result,4)'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'variance'
if _fn_name:
    if "Solution" in ns:
        try:
            _obj = ns["Solution"]()
            if hasattr(_obj, _fn_name):
                _target = getattr(_obj, _fn_name)
        except Exception:
            _target = None
    if _target is None and _fn_name in ns and callable(ns[_fn_name]):
        _target = ns[_fn_name]
# Fallback: if there's exactly one user-defined function, use it
if _target is None:
    _cands = [v for k, v in ns.items() if callable(v) and getattr(v, "__module__", "") in ("__judge__", "__main__")]
    _user_funcs = [c for c in _cands if getattr(c, "__name__", "").startswith("_") is False]
    if len(_user_funcs) == 1:
        _target = _user_funcs[0]
if _target is None:
    raise RuntimeError(f"Could not resolve callable '{_fn_name}'")

_raw = sys.stdin.read().strip()
if _raw:
    _parsed = json.loads(_raw)
    if isinstance(_parsed, dict):
        _kwargs = _parsed.get("kwargs", {})
        _args = _parsed.get("args", [])
    else:
        _args, _kwargs = _parsed, {}
else:
    _args, _kwargs = [], {}
if not isinstance(_args, (list, tuple)):
    _args = [_args]
_res = _target(*_args, **_kwargs)
try:
    sys.stdout.write(repr(_res) + "\n")
except Exception:
    pass

```

Measured memory_bytes: 5698