I just replicated this analysis.  I think you might have made some mistakes. 

I took a random sample of non-redirect articles from English Wikipedia and compared the byte_length (from database) to the content_length (from API, tags and comments stripped).

I get a pearson correlation coef of 0.9514766.

See the attached scatter plot including a linear regression line.  See also the regress output below. 

lm(formula = page_len ~ content_length, data = pages)

   Min     1Q Median     3Q    Max 
-38263   -419     82    592  37605 

                Estimate Std. Error t value Pr(>|t|)    
(Intercept)    -97.40412   72.46523  -1.344    0.179    
content_length   1.14991    0.00832 138.210   <2e-16 ***
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 

Residual standard error: 2722 on 1998 degrees of freedom
Multiple R-squared: 0.9053, Adjusted R-squared: 0.9053 
F-statistic: 1.91e+04 on 1 and 1998 DF,  p-value: < 2.2e-16

On Fri, Aug 2, 2013 at 12:24 PM, Floeck, Fabian (AIFB) <fabian.floeck@kit.edu> wrote:
to whoever is interested in this (and I hope I didn't just repeat someone else's experiments on this):

I wanted to know if a "long" or "short" article in terms of how much readable material (excluding pictures) is presented to the reader in the front-end is correlated to the byte size of the Wikisyntax which can be obtained from the DB or API; as people often define the "length" of an article by its length in bytes.

TL;DR: Turns out size in bytes is a really, really bad indicator for the actual, readable content of a Wikipedia article, even worse than I thought.

We "curl"ed the front-end HTML of all articles of the English Wikipedia (ns=0, no disambiguation, no redirects) between 5800 and 6000 bytes (as around 5900 bytes is the total en.wiki average for these articles). = 41981 articles.
Results for size in characters (w/ whitespaces) after cleaning the HTML out:
Min= 95 Max= 49441 Mean=4794.41 Std. Deviation=1712.748

Especially the gap between Min and Max was interesting. But templates make it possible.
(See e.g. "Veer Teja Vidhya Mandir School", "Martin Callanan" -- Allthough for the ladder you could argue that expandable template listings are not really main "reading" content..)

Effectively, correlation for readable character size with byte size = 0.04 (i.e. none) in the sample.

If someone already did this or a similar analysis, I'd appreciate pointers.



Karlsruhe Institute of Technology (KIT)
Institute of Applied Informatics and Formal Description Methods

Dipl.-Medwiss. Fabian Flöck
Research Associate

Building 11.40, Room 222
KIT-Campus South
D-76128 Karlsruhe

Phone: +49 721 608 4 6584
Fax: +49 721 608 4 6580
Skype: f.floeck_work
E-Mail: fabian.floeck@kit.edu
WWW: http://www.aifb.kit.edu/web/Fabian_Flöck

KIT – University of the State of Baden-Wuerttemberg and
National Research Center of the Helmholtz Association

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