Easy and Diffiult groups

Here's a thread I had opened in the German forum, but I guess this is the right section for it. I tried to move the thread to this section but wasn't able to figure out how its done, so I am reposting it here.

https://www.bigsoccer.com/forum/showthread.php?t=1274067

Here is a simple excel based analysis to see how 'easy' and 'difficult' groups have been ever since the WCs began in the 1930s.

The Assumptions
1) The difficulty or ease of a group is not decided by how the group appears on paper, or any other such preconceived notions. Difficulty is solely decided by how the teams perform actually during a group game.
2) A difficult group is one where the disparity in the strength of the teams is the least and not necessarily a team which has 2 world cup contenders. for eg, Italy, Brazil, Bhutan and Laos is not a difficult group, but one with Liechtenstein, Luxembourg, Andorra and San Marino is.

The Procdeure
Group match scores from all world cups were collated. (except for 1934 and 1938 because those WCs didn't have group matches). The mean of the goal differences in all the group games for each world cup were calculated.These are called the 'overall means' So were the standard deviations. After this, the means and standard deviations of goal differences of the world cup groups for 8 major (current) nations - Argentina, Brazil, England, France, Germany, Italy, Netherlands and Spain were collated. this too was done for all the world cups.


The Inference
If we find that the average of goal difference in a particular world cup for a nation are lower than that of the overall average, then we can conclude that the nation has had a 'difficult' group. If the same average is higher, we conclude that the group is easier ( relative to that world cup). I took a difference of 0.1 on either side of the overall mean to be insignificant. I.e if the overall goal difference average in a world cup is 2.33 and Germany's group averages 2.29, then the group is neither easy nor difficult. If Germany's group averages 2.55, then the group is easy and if Germany's group averages 1.96, then it is a difficult group.

Another way of determining the ease/difficulty of a group from the overall average is to test the data (nation wise) a set level of significance against the overall average for a WC. But that would have been extremely tedious and overtly statistical.

This is the excel sheet:
http://www.megafileupload.com/en/fil...lysis-xls.html

The Observations

This graph says it all
http://img707.imageshack.us/img707/9190/graphx.jpg

Here the bold blue line represents the overall goal difference average across the world cups. Surprisingly it is Germany and Argentina who has had the easier groups over the years and England and Italy the more difficult ones.

Here are how the major countries line up in WCs from 1954:

Country ( easy groups/ appearances)
Argentina (8/12)
Brazil (6/14)
England (0/11)
France (2/9)
Germany (10/14)
Italy (4/13)
Netherlands (2/6)
Spain (4/9)

What say?

PS: All mistakes are mine