Using Credible Sources

Learning Objectives

Course Objective for this section: Select, evaluate, and utilize discipline-specific information and literature to explore topics.

  • Differentiate between questions that can and cannot be answered using science.
  • Identify appropriate credible sources of information to research a topic.
  • Evaluate sources of information for their strengths and weaknesses.


Science is a very specific way of learning, or knowing, about the world. Humans have used the process of science to learn a huge amount about the way the natural world works. Science is responsible for amazing innovations in medicine, hygiene, and technology. There are however, areas of knowledge and human experience that the methods of science cannot be applied to. These include such things as answering purely moral questions, aesthetic questions, or what can be generally categorized as spiritual questions. Science has cannot investigate these areas because they are outside the realm of material phenomena, the phenomena of matter and energy, and cannot be observed and measured.

Questions that can be

answered using science

Questions that cannot be

answered using science

·       What is the optimum temperature for the growth of E. coli bacteria?

·       Do birds prefer bird feeders of a specific color?

·       What is the cause of this disease?

·       How effective is this drug in treating this disease?

·       How tall is Santa Claus?

·       Do angels exist?

·       Which is better: classical music or rock and roll?

·       What are the ethical implications of human cloning?

 Since this is a biology class, we will be focusing on questions that can be answered scientifically. Remember that in the scientific process, observations lead to questions. A scientific question is one that can be answered by using the process of science (testing hypotheses, making observations about the natural world, designing experiments).

Sometimes you will directly make observations yourself about the natural world that lead you to ask scientific questions, other times you might hear or read something that leads you to ask a question. Regardless of how you make your initial observation, you will want to do research about your topic before you start setting up an experiment. When you’re learning about a topic, it’s important to use credible sources of information.

Types of Sources

Whether conducting research in the social sciences, humanities (especially history), arts, or natural sciences, the ability to distinguish between primary and secondary source material is essential. Basically, this distinction illustrates the degree to which the author of a piece is removed from the actual event being described. This means whether the author is reporting information first hand (or is first to record these immediately following an event), or conveying the experiences and opinions of others—that is, second hand. In biology, the distinction would be between the person (or people) who conducted the research and someone who didn’t actually do the research, but is merely reporting on it.

Primary sources

These are contemporary accounts of an event, written by someone who experienced or witnessed the event in question. In general, these original documents (i.e., they are not about another document or account) are often diaries, letters, memoirs, journals, speeches, manuscripts, interviews, photographs, audio or video recordings, or original literary or theatrical works.

In science, a “primary source” or the “primary literature” refers to the original publication of a scientist’s new data, results, and conclusions. These articles are written for other experts in a specific scientific field.

You’ve probably done a writing assignment or other project during which you have participated in a peer review process. During this process, your project was critiqued and evaluated by people of similar competence to yourself (your peers). This gave you feedback on which to improve your work. Scientific articles typically go through a peer review process before they are published in an academic journal. In this case, the peers who are reviewing the article are other experts in the specific field about which the paper is written. This allows other scientists to critique experimental design, data, and conclusions before that information is published in an academic journal. Often, the scientists who did the experiment and who are trying to publish it are required to do additional work or edit their paper before it is published. The goal of the scientific peer review process is to ensure that published primary articles contain the best possible science.

Secondary sources

The function of a secondary source is to interpret the primary source. A secondary source can be described as at least one step removed from the event or phenomenon under review. Secondary source materials interpret, assign value to, conjecture upon, and draw conclusions about the events reported in primary sources. These are usually in the form of published works such as magazine articles or books, but may include radio or television documentaries, or conference proceedings.

Popular vs. Scholarly Sources

Broad range of topics, presented in shorter articles Specific, narrowly focused topics in lengthy, in-depth articles
Articles offer overview of subject matter; interpretation, rather than original research; sometimes contain feature articles and reports on current social issues and public opinion Articles often contain previously unpublished research and detail new developments in field
Intended to attract a general readership without any particular expertise or advanced education Intended for specialist readership of researchers, academics, students and professionals
Written by staff (not always attributed) or freelance writers using general, popular language Written by identified specialists and researchers in subject area, usually employing technical, subject-specific language and jargon
Edited and approved for publication in-house (not peer-reviewed) Critically evaluated by peers (fellow scholars)   in field for content, scholarly soundness, and academic value
Articles rarely contain references or footnotes and follow no specific format Well-researched, documented articles nearly always follow standard format:

abstract, introduction, literature review, methodology, results, conclusion, bibliography/references

Designed to attract eye of potential newsstand customers: usually filled with photographs or illustrations, printed on glossier paper Sober design: mostly text with some tables or graphs accompanying articles; usually little or no photography; negligible, if any, advertising; rarely printed on high-gloss paper
Each issue begins with page number ‘1’ Page numbers of issues within a volume (year) are usually consecutive (i.e., first page of succeeding issue is number following last page number of previous issue)
Presented to entertain, promote point of view, and/or sell products Intended to present researchers’ opinions and findings based on original research
Examples: Newsweek, Rolling Stone, Vogue Examples: Science, Nature, Journal of Microbial and Biochemical Technology

 In science, it is often extremely difficult to read and understand primary articles unless you are an expert in that specific scientific field. Secondary sources are typically easier to read and can give you the important information from a primary source, but only if the secondary source has interpreted the information correctly! It is always better to go to the primary source if possible because otherwise you are relying on someone else’s interpretation of the information. However, it is always better to use a source that you can read and understand rather than a source that you can’t. For this reason, it is very important to be able to identify credible secondary sources.

Evaluating Credibility

When you write a scientific paper (or any paper, really), you want to back up your statements with credible sources. You will need to identify credible sources to help you research scientific topics to help you develop interesting scientific questions. You will also need sources to help you form a well-educated hypothesis that is not just based on your guess about what will happen. A credible source is one that is trustworthy from which the information can be believed. Credible sources are written by people who are experts in the field (or at least are very knowledgeable) about the subject that they are commenting on.

We will be using a variation of the CRAAP test to help you determine whether or not sources that you find are credible or not. The CRAAP Test was created by Sarah Blakeslee, of the University of California at Chico’s Meriam Library. It is adapted below. When evaluating the credibility of sources using this method, if it’s CRAAP, it’s good!

You can use the table below to help you evaluate the credibility of your sources.

Credibility Table

Factors to consider Least reliable 

(0 points)

Possibly reliable

(1 point)

Most reliable

(2 points)

Currency No date of publication or revision given Outdated for this particular topic Recently published or revised
Reliable source Unreliable website, no additional info available Possibly reliable Official government or organization, institutional sites, academic journals
Author No author is given / the author is not qualified to write about this topic Author is educated on topic or is staff of an organization assumed to be knowledgeable on this specific topic Specifically identified expert in this field with degrees / credentials in this subject
Accuracy No review process and information is not supported by evidence from cited sources The information may have been reviewed or edited by someone knowledgeable in the field. It mentions but does not directly cite other sources The information has been peer reviewed and is supported by evidence from cited credible sources
Purpose Obviously biased or trying to sell you something Sponsored source; may present unbalanced information Balanced, neutral, presents all sides of the issue fully

In general, do not use a source if it doesn’t pass the CRAAP test! For our purposes, do not use any sources that score less than 6 points using the credibility table.

Several examples are given below for sources that you might come across if you were researching the topic of vaccine safety.

Example 1:

CDC (Centers for Disease Control and Prevention). Aug 28, 2015. Vaccine Safety [Internet]. [cited May 12, 2016]. Available from:

  Score Discussion – why did you give that score?
Currency 2 Aug 28 2015 is recent and shows that this information is updated frequently.
Reliable source 2 I looked at the “about this organization” and learned that the CDC is a major government organization that works to protect Americans from health, safety, and security threats. They are a division of the US department of health and human services.
Author 1 A specific author was not identified, but the page states that the content is from the CDC, which suggests that it was written by a knowledgeable staff member.
Accuracy 1.5 No information is given about the review process, but it was probably edited by staff at the CDC. There is a list of citations and links to primary scientific articles supporting the information.
Purpose 2 The point of view does not appear to be biased because it seems to be presenting factual information. Admittedly, it only presents the pro-vaccine side of the argument. There are no ads on the page or other information trying to change the reader’s viewpoint.
Credibility Score 8.5/10 This seems like an excellent source to use for research. It’s readable and I could look at the primary articles if I wanted to check them out.

Example 2: 

Stop Mandatory Vaccination. N.d.. The Dangers of Vaccines and Vaccinations [Internet]. [cited May 12, 2016]. Available from:


  Score Discussion – why did you give that score?
Currency 1 The copyright is given as 2015, but there is no date for this specific article. It does reference something that took place in 2015, so it is likely written after that.
Reliable source 0 The “About” page states that the organization was started by Larry Cook using a GoFundMe platform
Author 0 Larry Cook has been devoted to the natural lifestyle for 25 years, but doesn’t appear to have any degrees or specific expertise on this topic. Other contributing authors include Landee Martin, who has a Bachelor’s of Science in Psychology (which isn’t related to vaccine safety), and Brittney Kara, who is a mother who has studied holistic living for the last 17 years. None of the individuals specifically identified on the website appear to be experts in the field.
Accuracy 0.5 It seems unlikely that there is any review process. There are links to several sources, but none of them appear to be primary scientific articles. Several are links to interviews.
Purpose 0 This source is extremely biased. Even the name of the website is biased. There is a link to donate to the webpage. There are at least 10 ads for anti-vaccine books and websites.
Credibility Score 1.5/10 I would not want to use this source to research this topic. It’s extremely biased and doesn’t seem to offer much evidence for its assertions.

Citing Your Sources

One of the goals for any class is to help students become better scholars. And, one of the important skills of scholarship is proper citation of resources used. Citations demonstrate your “credentials” as a scholar, and provide a resource to your readers of good reference material.

Why do you have to cite your sources?

No research paper is complete without a list of the sources that you used in your writing.  Scholars are very careful to keep accurate records of the resources they’ve used, and of the ideas and concepts they’ve quoted or used from others. This record keeping is generally presented in the form of citations.

A citation is a description of a book, article, URL, etc. that provides enough information so that others can locate the source you used themselves. It allows you to credit the authors of the sources you use and clarify which ideas belong to you and which belong to other sources. And providing a citation or reference will allow others to find and use these sources as well.  Most research papers have a list of citations or cited references and there are special formatting guidelines for different types of research.

However, there are many “proper” formats because each discipline has its own rules. In general we ask only that you use one of the “official” formats and that you use it consistently. To understand what we mean by “consistent”, compare the citations in two scientific journals. You will notice that each journal has its own rules for whether an article title is in quotes, bold, underlined, etc., but within each journal the rule applies to all reference citations. Below is a condensed guide to the general format used in science (CSE). For more detailed information consult one of the online citation guides and generators.


Plagiarism is presenting the words or ideas of someone else as your own without proper acknowledgment of the source. When you work on a research paper you will probably find supporting material for your paper from works by others. It’s okay to quote people and use their ideas, but you do need to correctly credit them. Even when you summarize or paraphrase information found in books, articles, or Web pages, you must acknowledge the original author. To avoid plagiarism, include a reference to any material you use that provides a fact not commonly known, or whenever you use information from another author.  In short, if you didn’t collect the data or reach the conclusion on your own, cite it!

These are all examples of plagiarism:

  • Buying or using a term paper written by someone else.
  • Cutting and pasting passages from the Web, a book, or an article and insert them into your paper without citing them. Warning! It is now easy for your instructors to search and identify passages that you have copied from the Web.
  • Using the words or ideas of another person without citing them.
  • Paraphrasing that person’s words without citing them.

 Tips for Avoiding Plagiarism:

  • First, use your own ideas—it should be your paper and your ideas should be the focus.
  • Use the ideas of others sparingly—only to support or reinforce your own argument.
  • When taking notes, include complete citation information for each item you use.
  • Use quotation marks when directly stating another person’s words. Quotes are not frequently used in scientific writing unless you are directly quoting someone’s spoken words.

Citing Sources in CSE Format

The Council of Science Editors (CSE) citation format is commonly used in scientific writing. CSE format emphasizes the information that is important when writing scientifically: who wrote the information and when they wrote it. In different fields, there is an emphasis on different types of information. In the humanities, MLA format is commonly used. This style emphasizes the author’s name and the page number. This information allows a reader to track down the exact quotes that are being discussed. Another commonly used format, APA, emphasizes the author’s name and the year the information was published.

The standard format for citing a source in science writing is the Name-year format. In this format, the first author’s last name is followed by the date. For example:  Not all populations of alligators in the everglades are at risk from habitat loss (Nicholson, 2002).

If you are not familiar with the CSE citation style, you can get additional information and examples at

Beware of computerized “citation creators.”  While they can get you part way to a correct citation, they rarely are 100% correct.  For example, they often fail to put the last name first.


Citing a scientific journal article

Author’s last name first initial, next author’s last name first initial. Date published. Title of Article. Journal Name. Volume (issue): pages.

Please note that you need to cite the JOURNAL, not the DATABASE that you got it from. Citing the database in which you found a scientific journal article is like citing Google for an internet resource that you are using.

Flores-Cruz Z, Allen C. 2011. Necessity of OxyR for the hydrogen peroxide stress response and full virulence in Ralstonia solanacearum. Appl Environ Microbiol. 77(18):6426-6432.

Werling BP, Lowenstein DM, Straub CS, Gratton C. 2012. Multi-predator effects produced by functionally distinct species vary with prey density. J Insect Sci; 12(30): 346-378.

Shriner, W.M. 1998. Yellow-bellied marmot and golden-mantled ground squirrel responses to heterospecific alarm calls. Animal Behaviour 55:529-536.

Citing an internet resource

Author’s last name, first initial. Date published. Title of Website [Internet]. Publisher information. [cited on date that you accessed the information]. Available from: URL where you accessed the source.

Williamson RC. 2004. Deciduous tree galls [Internet]. Madison (WI): University of Wisconsin-Madison; [cited 2013 Sep 12]. Available from

[BP] The Biology Project. 2003. The chemistry of amino acids [Internet]. University of Arizona; [cited 2004 Mar 17]. Available from:

Hilton-Taylor C, compiler. 2000. 2000 IUCN red list of threatened species [Internet]. Gland (Switzerland) and Cambridge (UK): IUCN; [cited 2002 Feb 12]. Available from:

Citing Sources Within Text

We will be using the CSE Name-year format for citations. When you want to provide a citation reference for a statement that you are making, you should end the sentence with (First author’s last name, year). If the article was written by an organization and not a specific author, you can use the name of the organization (or an abbreviation for the name).

Example: Sickle cell anemia is caused by abnormally-shaped haemoglobin proteins (NIH, 2012).

In the References Cited section (a.k.a. Literature cited…) list all the sources you cited in your paper, but do not include any items that you did not specifically cite within the body of your paper or project, even if you read them!  Except in rare instances, do not cite a reference that you have not personally read.

You should then list all your references in the Literature Cited section alphabetically by author’s last name.

For more information and lots of examples of what to do in specific instances, please visit


“Cite Your Sources” by University of California, Santa Cruz, University Library is licensed under CC BY 3.0

“What is plagiarism?” by University of California, Santa Cruz, University Library is licensed under CC BY 3.0

“Distinguish Between Primary and Secondary Sources” by University of California, Santa Cruz, University Library is licensed under CC BY 3.0

“Distinguish between Popular and Scholarly Journals” by University of California, Santa Cruz, University Library is licensed under CC BY 3.0


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Principles of Biology Copyright © 2017 by Lisa Bartee, Walter Shriner, and Catherine Creech is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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