Only a Small Part of Work is Relevant
When only a small part of someone else's work is relevant, such as a statistic or quote, it need only be summarized or quoted. However, it is important to inform your audience when that work, as a whole, does not support your point or isn't relevant. The best way to work with data or information from an outside source is to provide a short, context-setting summary of the entire piece and only the detail of what is relevant to your argument.
This summary can be as little as a phrase or clause. For instance:
Although Smythe is against multicultural education in general...
It can also be an entire sentence as:
In Back to the Basics Smythe argues for a common curriculum for all students. Some of his examples, however, can also support the exact opposite conclusion.
After such a context-setting phrase or sentence, you are free to summarize only those points you intend to use. For example:
Although a discussion of recycling forms only a small part of Harrison's argument about global warming, his statistics on recycling are directly relevant here. As Harrison reports, although 60% of American families recycle in some way, only 2% of that 60% recycle all of their recyclable waste.