Scenario Planning and Evaluation

I work currently as IT Manager and I would like to know more about methodologies and techniques to Plan and Evaluate a Scenario. An Scenario is the modelling of some partial or total process breaking it into several variables:
1. Time,
2. Cost,
3. Quality,
4. Human Resources,
and other variables like:
1′. External Agents,
2′. Internal Agents,
3′. Standard Parameters,
4′. NonsStandard Parameters.

If a project manager detects this 8 variables and he / she asign each one a punctuation,can assign priorities based on this analysis.

I would like to know if there is someone working with an Scenario Evaluation or Analysis’ methodology.

Regards,

Daniel.