ITForum Question Posted...Analysis phase for Web based training question

I finally decided to post a question to the ITForum community to see how many responses I receive and the quality of the responses. I'm excited to see the experiences shared from others that I can actually put to some good use on my current project at work. I'm finding that these Professional Learning Communities are social networking groups that promotes knowledge sharing. Let's see what happens....

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IT Forum Family,

I am a PhD student at the University of Alabama in Tuscaloosa and also work as a consultant where I recently joined a project as an Instructional Designer. We are in analysis phase for developing training modules (web based) for approximately 1200 employees. For those of you that have experience in this area, what has been the rule of thumb for an acceptable time duration for a module that the learner will retain the material? Do any of you have any sites you can direct me to research more on this phase?

Any input would be appreciated.