Timeline for Find an approximate expression of a sum of a product using the average of each item
Current License: CC BY-SA 3.0
7 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Oct 2, 2014 at 13:16 | vote | accept | Changwang Zhang | ||
| Apr 20, 2012 at 5:37 | comment | added | Gerry Myerson | @Barry, right you are, of course. | |
| Apr 19, 2012 at 23:37 | comment | added | Barry Cipra | @Gerry, I think you mean $\langle x \rangle$, not $n\langle x \rangle$, too (see my comment to Aaron Meyerowitz's answer). I'm not sure why the OP bothers putting what amounts to an $n\langle k \rangle$ in the denominator of what he wants to express in terms of $\langle k \rangle$ etc. | |
| Apr 19, 2012 at 6:11 | answer | added | Aaron Meyerowitz | timeline score: 2 | |
| Apr 18, 2012 at 23:39 | comment | added | Gerry Myerson | $n\langle x\rangle$ is a (trivial) upper bound, and is attained when the $x_i$ are all equal, regardless of the distribution of the $k_i$. | |
| Apr 18, 2012 at 19:18 | comment | added | Gerhard Paseman | Approximate, yes. Meaningful? Unlikely. Take a long bar and divide it into n varying commensurable lengths, one length for each k_i. The average of the square values gives some information, I saynot enough: take the average of the x's to be 1/2, then color the 1/2 shortest segments one color, and the remaining longest segments another. That represents your variability when you know the average x value. The square average may weakly measure that variability, but it does not say where the desired value (sum of colored lengths) lives. Gerhard "Ask Me About System Design" Paseman, 2012.04.18 | |
| Apr 18, 2012 at 18:51 | history | asked | Changwang Zhang | CC BY-SA 3.0 |