Internal Assessment · 7 min read
Sources for your IB IA and EE: where to find them, how to judge them, how to cite them
Fewer, better sources, each doing a clear job in your IA or EE, and referenced so a reader can find every one.
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Good sources for an IB IA are a handful of credible ones, each doing a specific job: explaining the theory behind your hypothesis, justifying your method, and giving you published values or findings to compare your result with. Find them through Google Scholar, PubMed, your school's databases, government and NGO data portals and good textbooks. Every source you use must be cited where you use it and listed in a bibliography, in any consistent referencing style.
The IB is strict about the last part. The science subject guides treat missing or improper referencing as malpractice, and the IB's academic integrity policy expects you to acknowledge other people's ideas, words, images and data in the body of the text, not just at the end.
Where do I find sources that will hold up?
| Where | Good for | How to use it well |
|---|---|---|
| Google Scholar | Research papers in any subject | Click "Cited by" to find newer work on the same question; "All versions" often leads to a free PDF |
| PubMed | Biology, medicine, psychology | Use the "Free full text" filter; read the methods, not just the abstract |
| School databases (JSTOR, EBSCO and similar) | Peer-reviewed articles your school subscribes to | Ask your librarian which ones you can use and how to log in from home |
| Government, UN and NGO data | ESS, Global Politics, database-based science IAs | National statistics offices, meteorological services, the World Bank, WHO and GBIF (species records) publish raw data you can analyse yourself |
| Textbooks and the data booklet | Established theory and accepted values | A good source for an enthalpy value or a standard mechanism; not for recent findings |
| Professional and scientific bodies | Standard methods, safety, reviews | Learned societies and national academies publish accessible, reliable summaries |
Search with the terms researchers use, not the ones in your head. "Effect of temperature on catalase" finds school websites; "catalase thermal inactivation kinetics" finds papers. Reading one good paper's introduction and reference list is often faster than ten searches.
How do I tell whether a source is good enough?
Acronym checklists help you remember to ask questions, but they don't answer them. Work through these for any source your argument relies on:
- Who wrote it, and would they know? A named researcher in the field, a government agency or an editorial team is accountable; an anonymous page isn't.
- Where was it published? Peer-reviewed journals, academic publishers and official bodies check work before publishing. Blogs, revision sites and company pages don't, or have something to sell. Preprints (on bioRxiv, for example) are real research that hasn't been reviewed yet; say so if you cite one.
- Is it the original? A news article about a study is a summary of a summary. Trace the claim back to the study and cite that.
- Does it show its evidence? Look for methods, sample sizes and data. A claim with no visible evidence is an opinion.
- Do its conditions match yours? An optimum temperature for a thermophilic bacterium's enzyme tells you little about catalase in potato. Species, temperature, pH and population all matter.
- Is its age a problem? A 1950s paper on enzyme kinetics can still be the right citation; a 2012 figure for smartphone use is out of date.
- Does it agree with other sources? If not, that disagreement is worth a sentence in your IA, with your view on why.
Chatbots produce plausible text and sometimes invent references that look real. If an AI tool points you to a claim or a paper, find and read the original yourself, and cite that. How to acknowledge AI use itself is covered in using AI in the IA.
What should sources actually do in an IA?
Each source should earn its place in one of three jobs.
1. Background: why you expect what you expect
The theory that leads to your hypothesis. In a science IA this is where you explain, with citations, why temperature should affect enzyme activity in the way you predict. Keep it to theory that your conclusion will come back to. Your research question sets the boundary.
2. Methodology: why your method is sound
Sources that justify choices: a standard assay you adapted, a published range of concentrations, a sampling technique used in fieldwork studies. "The DCPIP titration method was adapted from [source]" shows the reader you didn't invent the procedure from nothing, and gives them somewhere to check it.
3. Comparison: what your result means
This is the use students most often skip, and it carries marks. The science Conclusion criterion rewards comparing your result with the accepted scientific context, which can come from published papers, data values or textbooks, and the guide asks that those citations be detailed enough to trace. ESS asks for traceable background research in its first criterion.
Loses marks"My value for the enthalpy of combustion of ethanol was lower than the real value because of heat loss."
Earns marks"My value of −760 ± 50 kJ mol−1 is 44% smaller in magnitude than the literature value of −1367 kJ mol−1 [citation]. Simple spirit-burner calorimetry is known to underestimate this value, mainly through heat loss to the surroundings and incomplete combustion [citation]. Both fit what I saw: soot on the can, and a gap far larger than my 6% uncertainty."
How many sources do I need?
There is no required number. For a 3,000-word science or ESS IA, somewhere around five to ten sources that each do one of the three jobs above is typical; an IA built on two textbook pages looks thin, and one listing 25 websites looks padded. An Extended Essay needs more depth and range, because the essay is built on research rather than on one experiment.
A useful test: could you say, for every entry in your bibliography, which sentence in your IA depends on it? If not, either use it properly or remove it.
How do I reference sources in an IB IA or EE?
Two parts, every time:
- In-text citation at the point of use: a short marker next to the idea, number or quotation you borrowed, such as (Bradford, 1976) in APA or a numbered footnote. Direct quotations also need quotation marks.
- Full entry at the end with enough detail for a reader to find the source.
The IB doesn't prescribe a style and leaves the choice to your school; any established one is fine if you apply it consistently. Some examples in APA:
- Journal article: Bradford, M. M. (1976). A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Analytical Biochemistry, 72(1–2), 248–254.
- Web page: Organisation or author. (Year). Title of page. Site name. URL (accessed day month year)
- Dataset: Organisation. (Year). Title of dataset [Data set]. URL (accessed day month year)
Always record the date you accessed an online source: the science and ESS subject guides require it for electronic sources, and it's good practice in any IA or EE. Images, graphs and data taken from a source need a citation in the caption, just like text.
Add each citation the moment you use a source, not at the end. A reference manager such as Zotero, or the citation tool in your word processor, saves you from hunting for a half-remembered page the night before the deadline.
Reference list or bibliography?
Strictly, a reference list contains only the sources you cited in the text, while a bibliography can also include sources you consulted but didn't cite. For an IA, a list of the sources you actually cited is what's needed, whichever heading your school uses; ask if you're unsure.
What should I avoid?
- Wikipedia as an authority. Use it to orient yourself and mine its references, then cite the originals you've read.
- Padding. Sources you never read, listed to look thorough. Teachers and moderators notice when the bibliography is longer than the engagement with it.
- Citing second-hand. Copying a reference from another paper's list without reading the original. If you only read the summary, cite the summary.
- Revision and homework sites for anything beyond basic definitions. Find the textbook or paper they paraphrase.
- Close paraphrasing. Swapping a few words in someone else's sentence can still count as plagiarism, even with a citation, because the wording is still theirs. Read, close the tab, then explain it in your own words and cite it.
- References you can't find. If you can't open a source and confirm it says what you claim, don't cite it. This is the main risk with AI-suggested references.
What changes for the Extended Essay?
The principles are the same; the scale and the scrutiny are higher. The essay depends on a wider range of sources, including some that disagree, and you are expected to evaluate them in the text, not just use them. Keep a record of every source and how you used it in your Researcher's Reflection Space as you go. Footnotes used purely for references don't count towards the 4,000 words, but footnotes that add content do. The Extended Essay guide covers the full process.
For how sources fit into a finished science report, see the References section of the annotated science IA example.
Questions students ask
Can I cite Wikipedia in my IA?
Use it to get oriented and to find sources in its reference list, then read and cite those originals. A Wikipedia page can change at any time and has no named, accountable author, so it is weak evidence for a claim your IA depends on. Some schools ban it outright.
Does the bibliography count towards the IA word count?
For the Biology, Chemistry, Physics and ESS IA, no: the subject guides exclude citations and the bibliography from the 3,000-word limit, along with tables, graphs, equations and headers. Check your own subject guide for other IAs.
Which referencing style does the IB want?
None in particular. Use the style your school or teacher agrees, such as APA, MLA or Harvard, and apply it consistently. What matters is that every borrowed idea is marked where you use it and listed in full at the end.
Do I need to cite my school's lab method or my textbook?
Yes. If your method is adapted from a school protocol, a practical guide or a published paper, say so and reference it. Textbooks are fine to cite for established theory.