All research - not just that from think tanks, needs to be evaluated for bias. Authors or organizations may have agendas that inform their writing; this can make some sources less credible than they first appear.
For example, certain news organizations have political tendencies; Fox News and the Wall Street Journal lean to the right, while MSNBC leans to the left.
While news organizations may not have explicit political agendas, some think tanks will. Before using research from a source, you should read the mission statement of the organization to assess the validity of the information you are reading.
For example, if you wanted to cite Americans for Tax Reform, reading their mission statement would quickly inform you that this organization's stated purpose is to oppose tax increases. This agenda likely informs any research they may provide.
Evaluating sources also extends to individuals you wish to cite. For example, if you are citing a legislator to support your argument, it is important to know whether or not that legislator has a political interest in supporting one side or another. If a legislator makes an argument against increasing agricultural regulations, and his biggest contributor is Monsanto (a multinational biotechnology company that produces herbicides), then his argument is less likely to be unbiased.
Debaters must perform research to gain a broad understanding of the issues they discuss.
Research can be conducted in a variety of ways, but the guiding principle should always be the same: research a subject to learn more about it. This sounds obvious, but many speakers make the mistake of seeking specific evidence to support a specific point; they write an argument, then look for a quotation or statistic to substantiate it. This type of research ultimately leads to a narrow and incomplete understanding of an issue.
A speaker who finds only three pieces of evidence to support her three arguments will be unprepared for questions and ill-equipped to answer the arguments her opponent makes. Instead, speakers should read and research to obtain a broad understanding of the issues involved in a topic.
Acceptable sources include: academic monographs; articles published by academic experts; reports from think tanks (like Cato, Heritage, and Brookings, though debaters should be wary of the bias inherent in many think tanks; Cato has a libertarian agenda, while Heritage leans to the right, and Brookings leans to the left); government reports (from the relevant organizations; if there is a bill about reducing crime, it would make sense to cite FBI statistics); articles from respected magazines (The Economist, Foreign Policy, Foreign Affairs, etc.); Supreme Court and appellate court rulings; and articles from reputable newspapers (New York Times, Washington Post, Wall Street Journal, etc.) are also acceptable.
Academic studies usually provide the most reliable evidence because they are written by qualified experts in the field, and they tend to have sound and well-explained methodologies. Debaters must realize that simply typing the topic into search engines and databases is unlikely to yield useful results. Debaters should take several steps when using these online resources. First, they should attempt to find the key terms used when discussing each topic. A key term is a specific phrase used by academics collectively to talk about a particular issue. For example, if a debater were discussing whether or not corporations have the right to fund political campaigns, he would discover that the term academics and the courts use to describe this right is “corporate personhood” and search using that term.