If you're thinking of heading back to school for a master's degree in business administration (MBA), you've probably wondered how it could change your paycheck.

It depends upon many variables, including which school you attend, your prior experience and whether you enroll in a full-time or part-time program, says Rachel Edgington, project manager in information services for the Graduate Management Admission Council (GMAC). GMAC, which administers the GMAT that graduate schools use to determine who gets into MBA programs, surveys past test takers to see where they end up and what they earn before and after graduation.

The Biggies

GMAC's ongoing research has found that these three factors affect MBA salary the most (in order of highest influence):

• Preexisting salary.
• Function of employer.
• Number of people managed (pre-MBA).

In reaching these conclusions, Edgington controlled for other factors that could influence salary levels, such as age, gender, program type, race or ethnicity, marital status, number of dependents, specialization, life values (the importance of wealth, financial security, work and family) and pre-MBA work experience (size of budget, number of people managed, years of experience and highest position held).

Experience Counts

The three factors add up to the following: An MBA won't guarantee you a job on Wall Street if you have no quantitative skills or experience to back it up. It's an issue David Petersam comes across often as president of AdmissionsConsultants Inc., a Vienna, Virginia, firm that helps business school applicants gain admission to suitable schools.

"Sometimes people get their hopes up about salaries when they get out of school," says Petersam. "If you don't have the background for investment banking, you don't want to be disappointed when Goldman Sachs won't touch you [after graduation].

You also have to match your temperament and interests to your postgraduation work. If you don't have the drive it takes to work extremely long hours, you won't like -- or do well in -- investment banking.

Likewise, you need to make sure an MBA is right for helping you reach your career goals. Petersam has counseled MBA wannabes who plan to use their degrees to become financial planners. He tells them they're going after the wrong degree and refers them instead to a financial planning certification program.

Where You Work

Both experts agree that consulting firms and the healthcare industry pay the highest salaries to newly minted MBAs. GMAC's data in a 2004 report show graduates working in consulting earned a median of $95,000 and those in healthcare a median of of $80,000. According to GMAC's 2008 Global MBA Graduate Survey, graduates entering the consulting industry had the highest salary rate increases, followed by the finance/accounting industry. Career changers also saw the biggest increases in consulting, followed by manufacturing and healthcare.

However, those figures, as well as salary data given out by graduate schools themselves, may be inflated for two reasons. First, the figures are self-reported, and who doesn't like to exaggerate a little? Second, salaries in banking can include big bonuses, so total compensation might be higher in that field depending upon what kind of year you have, Petersam says.

Perspective

Also according to GMAC's 2008 MBA graduate survey, graduates of full-time MBA programs expect about a 67 percent increase from their pre-MBA salaries.

And the results of GMAC's 2008 Corporate Recruiters Survey show that most MBA graduates could expect 2008 salaries "about 35 percent higher than that of other graduate school students and almost double the average starting salary of undergraduate school students."

Full-Time vs. Part-Time

Will your choice of programs make a significant difference in your post-MBA salary? Part-time students tend to enjoy a lower percentage increase in their salaries, possibly because part-time students typically have higher salaries to begin with.

While money is important, there's more than one way to judge the cost and benefit of pursuing an MBA, says Jeff Blum, founder of MBA Depot, an online networking site for MBA alums.

"For someone who wants to start his own business, the return is going to be different than someone who wants to go to a top-tier consulting firm," says Blum. "If you want to work on Wall Street, you don't want to go to a second-tier school, because those top employers aren't going to interview on your campus.