Depending on your aims, you might want to measure transfer to other problems: that is, do participants who used tool A for the sorting task, then do better when tackling a new problem, possibly with a different tool, than participants who used tool B?

You might also want to look at memory and savings: how do the participants manage two months later? Occasionally cognitive tasks like yours show no effect at the time but produce measurable differences when the same people do the same tasks later.

Pretty hard to create a truly fair test, but things to think about are controlling for practice and order effects, which should be easy, and controlling for experimenter expectation effects. The hardest thing to balance for is sometimes the training period: people using a new tool have to learn about it, and that gives them practice effects that the controls might not get. Sometimes people create a dummy task for the control condition to avoid that problem; or you can compare different versions of the tools, with differing features.

I suggest you try to avoid the simple A vs B design and instead look for a design when you can predict a trend: find A, B, C such that your theory says A > B > C. The statistical power is much better.

Don't forget to talk to the people afterwards and get their opinions. Sometimes you can find they weren't playing the same game that you were.

Good luck

Thomas Green

On 1 Mar 2011, at 11:20, Stefano Federici wrote:

Dear Collegues,
I need to plan an evaluation of the improvements brought by the usage of specific software tools when learning the basic concepts of computer programming (sequence, loop, variables, arrays, etc) and the specific topic of sorting algorithms.

Which are the best practises for the necessary steps? I guess the steps should be: selection of test group, test of initial skills, partition of the test group in smaller homogenous groups, delivery of learning materials by or by not making use of the tools, test of final skills, comparative analysis.

What am I supposed to do to perform a fair test?

Any help or reference is welcome.

Best Regards

Stefano Federici
Professor of Computer Science
University of Cagliari
Dept. of Education and Philosophy
Via Is Mirrionis 1, 09123 Cagliari, Italy
Tel: +39 349 818 1955 Fax: +39 070 675 7113

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