IB Psychology IA: Criteria, Word Count & How to Pass

By Michael Thompson · Former IB Diploma Programme coordinator; 10 years at Bromsgrove School · Published 4 September 2026

The IB Psychology IA is a simple experimental study in which you replicate a published piece of psychological research, write it up in no more than 2,200 words, and submit it for internal marking and external moderation. It counts towards your final Diploma grade and is assessed against four criteria: introduction, exploration, analysis, and evaluation. Unlike your exams, you have significant control over the topic, the design, and the pace - which makes early planning the biggest factor in how well it goes. This guide covers every criterion, the ethics rules, the statistics expected, and the most common mistakes students make.

Key Takeaways

• 2,200-word hard limit: The IB Psychology IA must not exceed 2,200 words; anything over that limit will not be read by your teacher or moderator.
• Four marked criteria: Introduction, exploration, analysis, and evaluation are each scored separately, and the marks are weighted differently, so weak evaluation costs you more than most students expect.
• Replication, not original research: You are not designing a new study from scratch - you are reproducing a published experiment with your own participants under controlled conditions.
• Ethics is examined, not just procedural: Informed consent, the right to withdraw, and participant debriefing must appear both in your procedure and in your written evaluation, or you lose marks in two criteria.
• Both descriptive and inferential statistics are required: Means, standard deviations, and an appropriate inferential test must all appear in the analysis section with correct interpretation.
• Choose a simple, ethically clean study: The most common high-mark IAs replicate well-known cognitive studies - not clinical, deceptive, or physiological ones - because the design stays manageable and the ethics stay unambiguous.

In This Article

1. What the IB Psychology IA actually is
2. IB Psychology internal assessment criteria explained
3. Choosing a study to replicate: what works and what doesn't
4. The ethics checklist every IB Psychology IA needs
5. Analysis: descriptive and inferential statistics for the IB Psychology IA
6. IB Psychology IA format and word count: what counts and what doesn't
7. Common mistakes that cost marks - and how to avoid them
8. What to do next

1. What the IB Psychology IA actually is

The IB Psychology IA is a short experimental report in which you replicate a previously published study, not design original research. You are not expected to create a novel hypothesis from scratch. Instead, you take an existing study, run a simplified version of it with a new sample, and write up your findings. That distinction matters: examiners are assessing your understanding of experimental method, not your creativity.

The report has a strict 2,200-word limit, and anything beyond that cut-off is not read or assessed by your teacher or the IB. Appendices, references, and raw data tables sit outside the word count, but every word inside your main sections does count, so there is no padding room.

Marking works in two stages. Your teacher marks the work first, then the IB externally moderates a sample of submissions to check that teachers are applying the rubric consistently, as the IB Diploma Programme specifies for internally assessed work. That moderation step is the reason alignment with the official criteria matters so much: if your teacher marks generously but your work does not meet the descriptors, scores can be adjusted downward.

One detail that catches students out: HL and SL students complete the same IA. There is no extended or separate HL component for the internal assessment itself. The differentiation between Higher Level and Standard Level sits in the examination papers, not here.

2. IB Psychology internal assessment criteria explained

!IB Psychology IA structure diagram showing four sections: Introduction, Exploration, Analysis, Evaluation with mark allocations.webp5680

The IB Psychology IA is marked against four criteria, each worth up to 6 marks, giving a total of 22 marks. Your teacher marks your work first, then the IB moderates a sample externally. Crucially, as the IB Diploma Programme confirms, this is a **criterion-related** system, not norm-referenced. You are judged against fixed descriptors, not ranked against your classmates. A strong cohort does not push your mark down.

Here is what the top band of each criterion actually requires:

A non-obvious point worth knowing: the IB Psychology internal assessment rubric treats operationalising variables as an exploration requirement, not an introduction one. Students who define their independent and dependent variables precisely in the introduction but then leave the procedure vague still lose exploration marks.

Evaluation is the most commonly penalised area. Generic statements such as "the sample size was small" score nothing without an explanation of how that specific limitation affected your specific results. Examiners look for the connection between the flaw and the data pattern you actually observed.

3. Choosing a study to replicate: what works and what doesn't

The single most consequential decision in your IB Psychology IA is which study you replicate. A strong choice makes every subsequent step easier. A poor choice creates problems that no amount of good writing can fix.

What the original study must have

Three conditions must all be met:

• A clearly defined independent and dependent variable. The IB Psychology internal assessment rubric rewards precise operationalisation, so if you cannot point to the IV and DV in the original paper's method section, the study is not a suitable model.
• Replicability in a school setting. You need student participants, a classroom or quiet room, and standard materials. Nothing that requires lab equipment, medical oversight, or specialist software your school does not own.
• Ethical cleanliness. The original study must use deception only where a brief, complete debriefing genuinely reverses any effect, and must involve no clinical populations, no participants under unusual psychological stress, and no physiological recording without medical supervision.

Studies that work well

Classic cognitive experiments are the safest ground. Word recall tasks (such as a replication of the Murdock serial position effect), Stroop-effect variants, and dual-coding studies all share two advantages: the variables are concrete and easy to operationalise, and the ethical risk is low. A counterintuitive quirk worth knowing: the Stroop task is so well-trodden that examiners see it constantly, which means a sloppily executed Stroop replication stands out more, not less. Execute it with rigour or pick a variant with a clearer rationale.

Studies that don't work

Avoid these categories outright:

• Studies using clinical or vulnerable populations (patients with depression, children under 12 without parental oversight structures your school cannot guarantee)
• Physiological measures such as heart rate, cortisol, or skin conductance
• Deception designs where participants cannot be fully restored to their prior state by debriefing
• Studies requiring specialist apparatus your school does not have

Operationalising variables: why specificity is the point

Operationalising variables means converting an abstract psychological construct into a specific, measurable procedure. "Memory" is a construct. "The number of words recalled correctly from a 20-item list after a 30-second retention interval" is an operationalised variable. The IB expects you to define both your IV and DV at this level of precision in your introduction and method.

The practical lesson is blunt: a simple study with tightly operationalised variables and clean data collection will outscore an ambitious replication riddled with confounds. Simpler, cleaner, better.

4. The ethics checklist every IB Psychology IA needs

Ethics in the IB Psychology IA is not a box-ticking exercise you handle in a single paragraph. The IB assesses ethical considerations explicitly in two separate criteria: the exploration section (where you describe your procedure) and the evaluation section (where you discuss limitations and propose modifications). Miss ethics in either place and you lose marks twice from the same oversight.

What you must include

Every IB Psychology IA requires all of the following:

• **Written informed consent** from each participant before data collection begins. If any participant is under 16, a parent or guardian must also sign.
• Right to withdraw stated clearly, with no penalty attached. Participants must know they can leave mid-study and that their data will be discarded on request.
• Full debriefing after data collection, including an honest explanation of the true aim if any concealment was used. The debrief is what makes mild concealment ethically defensible - without it, the concealment is simply deception.
• Anonymity and confidentiality of all data, stated to participants in advance.

What is not permitted

• Studies likely to cause psychological distress, even mild or temporary.
• Full uninformed deception where a proper debrief cannot reverse the effect on participants.
• Research involving vulnerable populations (children under 16 without explicit parental consent, people with diagnosed conditions, and similar groups).

A non-obvious gotcha: replicating a classic study does not automatically make your version ethical. Loftus and Palmer's original procedure is fine to replicate; a version that adds staged footage of real accidents would not be, regardless of how well the original is cited.

A consent form checklist you can build yourself

Produce two documents before you collect a single data point:

Consent form - include:

• Study title and researcher name
• A plain-language description of what participation involves
• Right to withdraw statement (explicit: "at any point, without penalty")
• Data anonymity statement
• Signature line and date

Debrief script - include:

• The true aim of the study
• Why any concealment was necessary
• Confirmation that the participant's data will be stored securely and anonymised
• Contact details if the participant has follow-up questions

Keep signed consent forms on file. Your supervisor may ask to see them.

5. Analysis: descriptive and inferential statistics for the IB Psychology IA

The analysis section of an IB Psychology IA has two distinct jobs: describe what the data shows, then test whether the difference between conditions is statistically significant. Keeping those two jobs separate is harder than it sounds.

Descriptive statistics

At a minimum, your analysis must include the mean and standard deviation for each condition, presented in a clearly labelled table. You also need at least one appropriate graph - a bar chart showing means with error bars is the standard choice for most replication studies, and examiners expect to see it.

The non-obvious point: standard deviation is not optional decoration. A mean without a measure of spread tells the examiner nothing about whether your two groups actually differed in any meaningful way. Students who report only means are leaving the analysis section structurally incomplete regardless of how tidy the table looks.

Inferential statistics

You must select and apply an appropriate statistical test and state whether the result is significant at your chosen probability level (typically p < 0.05). The choice of test is not arbitrary:

• Mann-Whitney U for independent measures designs with ordinal or non-normal data
• Wilcoxon signed-ranks for repeated measures designs with ordinal or non-normal data
• Parametric equivalents (independent t-test, related t-test) when your data genuinely meets the assumptions for interval-level measurement and normal distribution

Justify your choice explicitly. An examiner reading your ib psychology ia needs to see why that test fits your design and data type, not just the output.

Common analysis mistakes

• Reporting the mean only, with no standard deviation or variance measure
• Writing conclusions or interpretations in the analysis section - save those for the evaluation
• Selecting an inferential test without stating why it suits the design and measurement level
• Misreading the critical value table or omitting the critical value entirely when reporting significance

Finally: raw data belongs in an appendix and does not count toward your word limit. Pasting data tables into the main body wastes words and clutters the section examiners are marking.

6. IB Psychology IA format and word count: what counts and what doesn't

The 2,200-word limit applies to the main body of the report only. Several components sit outside that count, which matters more than it sounds: a thorough appendix can easily run longer than the report itself without costing you a single word.

Items typically excluded from the word count:

• Title page
• Abstract (if you include one)
• Reference list
• Appendices: raw data tables, blank copies of materials, consent forms, standardised instructions, and the debrief script

Always check the current IB Psychology subject guide for the definitive exclusion list, as the IB updates its guidance periodically and any discrepancy between a teacher's summary and the live guide will go against the student.

The standard report follows this order:

1. Introduction - rationale, theory, and the operationalised research hypothesis
2. Exploration (the method section) - design, participants, materials, procedure
3. Analysis (results) - descriptive statistics, inferential test, and your graph or table
4. Evaluation (discussion) - findings, limitations, modifications

One non-obvious point: the abstract and title page are not assessed under any criterion in the IB Psychology internal assessment rubric. Writing a polished abstract is not worth trading words you need in your Evaluation.

**APA 7 is the expected citation style** for the ib psychology ia. Your reference list must follow APA 7 formatting throughout, including hanging indents, author-date order, and DOI links where available. Examiners notice inconsistent referencing because it signals careless reading of sources, which reflects on the Introduction's credibility even if referencing is not a standalone criterion.

7. Common mistakes that cost marks - and how to avoid them

The IB Psychology IA rubric is specific enough that most mark losses are predictable. The same patterns appear repeatedly, and most of them are easy to fix once you know what the examiner is looking for.

Generic evaluation is the single biggest waste of marks. Writing "the sample size was small" scores nothing on its own. The examiner wants to know: small relative to what, and what specific distortion did that create in your data? A stronger version names the problem precisely, for example: "The sample of 20 sixth-form students skews toward high verbal IQ, which may have inflated recall scores compared to a community sample, making it difficult to generalise to the broader adolescent population."

Introductions that describe but do not connect. Many students spend several hundred words summarising Loftus and Palmer (or whichever study they replicated) and then introduce their own hypothesis as an afterthought. The examiner needs to see an explicit logical chain: original finding, your operationalised IV and DV, your directional or null hypothesis. If that chain is not stated, the Introduction criterion suffers regardless of how accurate the summary is.

Exploration sections that omit the null hypothesis or leave the IV and DV vague. Operationalising variables psychology-style means giving the exact measurement: not "memory" but "the number of correctly recalled words from a 15-item list after a 90-second delay." Without that precision, design and procedure descriptions read as a lab report rather than a psychology IA.

Unlabelled graphs. A bar chart without axis labels and a caption explaining what it shows in relation to the hypothesis earns no credit under Analysis, even if the statistical test underneath it is correct.

Exceeding the word count. Content beyond 2,200 words is not marked, full stop. This catches students who write a tight IA and then add a lengthy appendix discussion that accidentally falls inside the word-count boundary. Check where your examiner's word counter stops before submission.

8. What to do next

Most students delay choosing a replication study until the pressure is unbearable, then pick something vague and regret it. That delay is the single most damaging decision you can make, because every other element of the IA, your hypothesis, your operationalised variables, your chosen statistical test, depends on which study you replicate.

This week, do two things. First, go to the IB's official website and read the current IB Psychology subject guide for your exam session. Mark allocations and word-count exclusions do change between sessions, and your teacher's printed copy may be out of date.

Second, write one paragraph identifying the study you plan to replicate and explaining why it is feasible to replicate ethically within a school setting. That paragraph becomes the spine of your entire IA. Write it before the week is out.

FAQ

What is the IB Psychology IA?

The IB Psychology IA is a simple experimental study in which students replicate a published piece of psychological research with their own participants, write it up in no more than 2,200 words, and submit it for teacher marking and IB moderation.

When is the IB Psychology IA due?

The submission deadline is set by your school and coordinated with the IB's moderation calendar - typically in the first term of Year 2 of the Diploma Programme; check your school's internal deadline, which will fall before the IB's own moderation window.

What is the word count for the IB Psychology IA?

The main report must not exceed 2,200 words; appendices, the title page, references, and blank materials are typically excluded from this count, but students should verify the exact exclusions in the current IB Psychology subject guide.

Is the IB Psychology IA the same for HL and SL?

Yes - both HL and SL students complete the same experimental study IA with the same 2,200-word limit and the same four assessment criteria; the difference between HL and SL lies in the external exam papers, not the IA.

What inferential statistics are needed in the IB Psychology IA?

Students must apply an appropriate inferential statistical test - such as Mann-Whitney U for independent-samples designs or Wilcoxon for repeated-measures designs - and report whether the result is statistically significant, alongside descriptive statistics including means and standard deviations.

How does ethics affect the IB Psychology IA mark?

Ethical considerations must appear in both the exploration section (where you describe your procedure, including consent and debriefing) and the evaluation section (where you discuss limitations and modifications), so neglecting ethics can cost marks under two separate criteria.

References

• Assessment in the Diploma Programme - https://ibpublishing.ibo.org/extendedessay/apps/dpapp/guide.html?chapter=1&doc=d_0_eeyyy_gui_1602_1_e&part=6&section=1