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Percent Contribution

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QXL Monte Carlo New > Monte Carlo > Contribution Tools > Percent Contribution...

Decomposes the variation of each chosen output across the model's inputs, so the report says how much of an output's variation each input accounts for.

Three methods are offered, and you may run any combination of them. The dialog lists each with its own description; see Options.

One simulation per method

The engine computes one contribution method per simulation. Asking for all three is three simulations, and LMG dominates the time.

All three are given the same random seed, so wherever two methods use the same number of simulations they are computed on identical trials, and the comparison between the methods is not confounded by different random numbers.

It needs Fast Mode

A Percent Contribution run goes through the same path every simulation goes through, including the check that proves the engine against Excel before it is trusted.

A model that falls back to Native Mode produces no contribution table. Native Mode evaluates each trial through Excel and never reaches the code that computes contributions. That is reported to you rather than handed back as an empty report.

If that happens, run Validate Model, which names the exact formulas keeping the model out of the fast engine.

What it needs

At least one declared input and at least one output. A run with neither is refused before the dialog opens.

  • Options, for the three methods, the simulation counts and the seed.
  • Run Model, the ordinary simulation.
  • Validate Model, if the model will not run in Fast Mode.