Bias can create major problems in your paper without you noticing even during careful revision. Bias can be intentional or unintentional, and either way will do equal damage.
Intentional:
Sure you’re got your purpose. You want your readers to do something and you
sincerely believe it’s in their best interest. So what’s wrong with only giving
them the facts that you need them to hear? That will make your paper more effective,
right? And as this CD-ROM keeps telling you, that’s your goal in writing.
Here’s what’s wrong with it: First off, it’s unethical to intentionally mislead your readers, even when you think it’s for their good. Second, if they catch you—if they realize what you’re doing (as some of them are bound to do)—then you damage your ethos and lose your credibility.
Bias can show both in facts that you present (or don’t) and the way you present them. Of course you should take a stand, having a clear opinion will help readers to understand your point, but they should also know which parts are your opinion and which parts are facts.
If you leave out critical information and readers come across it after being convinced by your paper, they will have to reevaluate what they thought they knew. Someone else will have a chance to influence them away from your point of view. If you deal with those views in your paper, however, you guard against this by addressing those issues while building your ethos as readers trust you, realizing your effort to educate them fairly and openly. They will then feel more confident that they have made a wise and well-supported decision.
Unintentional:
Your beliefs and background may have taught to you accept that murder is
inherently wrong. If your audience agrees with you, you then have little or no need
to back up that assumption (helping readers to understand why
it's wrong can strengthen their resolve to act and they may appreciate the insight). You may also believe that sex outside
of marriage is inherently wrong, but if your audience disagrees with you or isn't yet sure
what to believe, you weaken your paper by failing to explain or otherwise back up your
point of view.
Take the time to carefully analyze your own values when working with sensitive or controversial issues. Back them up carefully if you expect readers to understand and consider or accept your views.
Scientific bias is another common problem you
may encounter.