Bound on k extreme values

Dependencies: None

Let $A = [a_1, a_2, \ldots, a_n]$ be $n$ numbers where $i < j \implies a_i \le a_j$.

Let $s = \sum_{i=1}^n a_i$, $x = \sum_{i=1}^k a_i$, $y = \sum_{i=n-k+1}^n a_i$. Then $x \le \frac{sk}{n}$ and $y \ge \frac{sk}{n}$.

Proof

\begin{align} & a_k \ge \frac{x}{k} \\ &\implies s = x + \sum_{i=k+1}^n a_i \ge x + (n-k)\frac{x}{k} = \frac{xn}{k} \\ &\implies x \le \frac{sk}{n} \end{align}

The proof of $y \ge \frac{sk}{n}$ is similar.

Dependency for:

  1. APS implies pessShare
  2. PROP implies WMMS and pessShare
  3. Additive chores and binary marginals
  4. Additive goods and binary marginals
  5. EF doesn't imply PROP for supermodular valuations
  6. 1BP: harmonic grouping

Info:

Transitive dependencies: None