def is_palindrome(text: str):
    for i in range(len(text)):
        if text[i] != text[len(text) - 1 - i]:
            return False
    return True
from typing import List
def mean_absolute_deviation(numbers: List[float]) -> float:
    mean = sum(numbers) / len(numbers)
    return sum(abs(x - mean) for x in numbers) / len(numbers)