Messages in this thread | | | Date | Mon, 21 May 2007 19:27:52 +0100 | From | Matt Keenan <> | Subject | Re: Sched - graphic smoothness under load - cfs-v13 sd-0.48 |
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Bill Davidsen wrote: > Ray Lee wrote: >> On 5/19/07, Bill Davidsen <davidsen@tmr.com> wrote: >>> I generated a table of results from the latest glitch1 script, using an >>> HTML postprocessor I not *quite* ready to foist on the word. In any >>> case >>> it has some numbers for frames per second, fairness of the processor >>> time allocated to the compute bound processes which generate a lot of >>> other screen activity for X, and my subjective comments on how >>> smooth it >>> looked and felt. >>> >>> The chart is at http://www.tmr.com/~davidsen/sched_smooth_01.html for >>> your viewing pleasure. >> >> Is the S.D. columns (immediately after the average) standard >> deviation? If so, you may want to rename those 'stdev', as it's a >> little confusing to have S.D. stand for that and Staircase Deadline. >> Further, which standard deviation is it? (The standard deviation of >> the values (stdev), or the standard deviation of the mean (sdom)?) >> > What's intended is the stddev from the average, and perl bit me on > that one. If you spell a variable wrong the same way more than once it > doesn't flag it as a possible spelling error. > > Note on the math, even when coded as intended, the divide of the > squares of the errors is by N-1 not N. I found it both ways in online > doc, but I learned it decades ago as "N-1" so I used that. N-1 is for estimating the standard deviation from a random sample of a population (s), N is for calculating the standard deviation of a whole population (σ).
xref http://en.wikipedia.org/wiki/Standard_deviation
Yes, I am aware of the potential for Wikipedia articles to be wrong, but this article seems correct at first blush :)
Matt
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