Mental Arithmetic This is very possibly not the best place to ask this, however it's the best I could find but please suggest anywhere else that might be better suited. 
I'm building a sort of challenge revolving around doing simple mental arithmetic (numbers between 1 - 100 using division, multiplication, addition and subtraction) in a set time period and grading based on number of correct answers in given period. 
In order to establish a baseline I'm looking for some information regarding how many correct mental arithmetic problems people can solve in, for example, 2 minutes. Ideally I'm trying to find the bell curve information on this (the lowest, average and best).
 A: There are people which they have different mental abilities to functionally produce answers to these mental arithmetic questions in under 2 minutes. Hence that the time will change depending on the mental abilities of the people in question.
I hope this answered your question.
A: Here's an initial sketch of what I would do:
People are too lazy for this. So, do it in reverse. Ahhhmm.  
In a Web application ("Are you smarter ?"), give users two abilities: 


*

*Take the test. (Largest weight on information gathered this way).  

*Browse through tests other "users" took, and show only the questions, the score/grade, and maybe the time it took to finish.  


With this, let the users (You choose one or more of these, and think of more):  


*

*Rank the "smartness" (significant weight, with the option to disregard at a later time)  

*Assert that they are smarter, i.e these are not so good test results (Minor weight, with the option to disregard at a later time). This would direct them to the beginning of a "similar" test (Large weight on this).

*Give the explicit option to take "this" test ("Similar") (Large weight on this). 


In actual tests you should gather as much information as you can, i.e, etc..
This is a feedback loop, initialized with fabricated users, tests, and results.  
Gradually/Slowly, it would/should:
1.  Be able to generate better tests (Better means many things here), e.g like choosing the best book to learn a given subject.
2. Make "Similar" test really more and more similar.
3. Make the statistics closer and closer to the objective unknown you are actually after, either by real empirical data, a clever summary of subjective data, or (Most probably) a clever combination of these...
