Active voice is an important matter when you are writing research articles. Here are few tips:
"...Active voice more closely resembles spoken language; hopefully ideal spoken language. When we speak, we generally use the active voice without thinking. Our writing should become that automatic.
You would never say:
Passive: My car (subject) was driven (action) to work by me.
Passive: Breakfast (subject) was eaten (action) by me this morning.
Instead, you would say:
Active: I (subject) drove (action) my car (object) to work.
Active: I (subject) ate (action) breakfast (object) this morning."
Source: Plain Language, http://www.plainlanguage.gov/howto/quickreference/dash/dashactive.cfm