If success for the Tesla Model S relied on so many variables being controlled, the very premise of the drive was questionable.

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Better yet, these products are so complex and involve so many variables--life span, tax rates, market performance, interest rates--that they're almost impossible for clients to evaluate properly.

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"There are so many variables that determine success, " he says.

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The tricky part about this topic is that you will need to revisit it periodically because there are so many variables and people will change their mind as the business grows and changes.

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Court records say it was often difficult for trucking companies to track how much money they were entitled to in Pilot rebates and discounts because there were so many variables in the company's diesel price discount program.

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Rather, with so many variables involved in qualifying for some forms of aid, and not knowing if that aid will come in the form of a student loan or a scholarship at most universities, perhaps more families will rise up to the challenge and create cool strategies to pay for college, with or without financial aid.

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There are so many unknown variables such as longevity, interest rates, market appreciation, and health care costs.

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With so many possible variables to consider, it makes sense to start with a clean slate and see what relationships we can tease out of the data.

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We often like to pigeonhole things but there are so many unknowns and variables.

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