Salary Survey Extra is a series of dispatches that give added insight into the findings of both our annual Salary Survey and our smaller Salary Survey PLUS polls. These posts contain previously unpublished Salary Survey data.

Remember the Reese's Peanut Butter Cups marketing campaign that told everyone that there's "no wrong way to eat a Reese's"? (Anyone else feel like half of everything they've ever managed to internalize in life is ad slogans?) Certification is sort of like that.

Not in the sense that certification is sweet and delicious, and that you should swipe all of the certifications out of your kids' trick or treat bags after they go to bed on Halloween. More in the sense that there are multiple means of preparing yourself to get certified, and no one of them is more "right" or "wrong" for a given learner than any of the others.

(Well, OK, brain dumps are a certification no-no, and they don't really help you do anything except maybe pass a multiple choice test.)

Some methods of certification preparation tend to be more useful (and more widely used) than others, however, and it can be helpful to know what tends to work best for most individuals. So in our recent Big Data Salary Survey, we asked survey respondents to tell us which study materials help them learn and prepare most effectively for their most recent certification.

Here's what we learned:

The Does Not Apply column is always interesting here, because it serves as a gauge of how many people actually do or do not use a given class of study materials, whatever they think of its overall effectiveness.

For example, more than half of all respondents have no use for boot camps or classes at the local community or technical college. On the other hand, although 55 percent of respondents just say not to online brain dumps, 45 percent used them at least enough to form an opinion of their usefulness.

Somewhat surprisingly, the Does Not Apply column also reveals that more than 90 percent of certified Big Data professionals committed to at least some level of preparation involving product documentation — reading the manual, in essence. Not even the reliably valued practice exams and self-study books can claim that breadth of usage.

On the other hand, both practice exams and self-study book have strong ratings of "excellent" or "very good." The champ in that regard, however, is the learn-by-doing approach of on-the-job training, rated excellent by 26.6 percent of respondents, and very good 37.6 percent of respondents. The best way to ensure success on your next Big Data certification exam, it would seem, is to get a Big Data job.