Candidate handbook
CPXS candidate handbook
Certified Product Experimentation Specialist
Everything that applies to the CPXS certification exam: what it covers, how the exam works, how it is scored and where to study.
Blueprint version 1, published on August 25, 2026. Study guide, edition 2026.1.
What the certification attests
For those who design and interpret product experiments: sizing, sensitivity and duration, threats to validity, reading results and launch decisions.
You design and interpret experiments
And you have noticed the hard part is not running the test: it is deciding the unit of randomisation and the metric before seeing any number.
You answer for the decision to launch or drop
The conclusion leaves your report and becomes product. When a result is inconclusive, you are the one explaining how that differs from "it does not work".
You have watched a test be read the wrong way
Stopping at the first significant reading, a finding in one segment out of eighteen, a comparison with last month. And you want the argument to refuse each one.
Prerequisite
None. You can take the certification exam directly.
Certification exam format
- Questions
- 50
- Duration
- 60 min
- Pass mark
- 70%
- Languages
- English, Portuguese, Spanish
The pass mark is fixed: you pass with 70% correct answers, with no curve and no comparison with other candidates.
Domains and weights
Questions are drawn for every certification exam, always in this proportion. The weights are the same the exam engine uses.
| Domain | Questions | Weight | Where to study |
|---|---|---|---|
1. Experiment design Which unit to randomise on, and why it is not always the unit where the effect appears. The plan declared before collection is what turns a test into proof. | 8 | 16% | Guide CPXS, chapter 4, Experiment design |
2. Metrics, instrumentation and unit of aggregation Which metric decides and which one holds the result. Aggregating by event, by session or by user changes the number and changes the conclusion on the same data. | 7 | 14% | Guide CPXS, chapter 5, Metrics, instrumentation and aggregation unit |
3. Sizing, sensitivity and duration The minimum detectable effect, and how to recognise that the test cannot answer the question before spending the weeks finding out. | 7 | 14% | Guide CPXS, chapter 6, Sample sizing, sensitivity and duration |
4. Threats to validity Interference between units, sample ratio mismatch, contamination from a model that learns from both groups at once, and novelty effect. | 8 | 16% | Guide CPXS, chapter 7, Threats to validity |
5. Analysis and interpretation of results Reading the confidence interval, not just the p-value. Daily peeking, multiple comparisons, subgroup findings, and significance against practical relevance. | 9 | 18% | Guide CPXS, chapter 8, Analysis and interpretation of results |
6. Methods without full randomisation Switchback by time window, geographic tests, difference in differences. And above all, what each of these methods does not let you conclude. | 5 | 10% | Guide CPXS, chapter 9, Methods without full randomization |
7. Decision and experimentation programme The launch criterion written before the result, and why win rate is the most quoted and least informative metric of a programme. | 6 | 12% | Guide CPXS, chapter 10, Decision and experimentation programme |
Certification exam rules
- Format
- Online certification exam, in your browser, with no scheduling and no exam centre. Questions describe work situations and ask for a decision. Some ask for more than one option, and the screen tells you how many.
- Time
- The clock runs on the server and starts when you open the certification exam. It does not pause: reloading the page, switching devices or closing the browser does not give time back. When time runs out, the exam is submitted with what you have answered.
- Navigation
- You can go back, change answers and flag questions for review. Before you finish, a screen shows what is answered, flagged and blank.
- Scoring
- Your score is compared with the pass mark, with no curve. A blank question counts as wrong, and multiple-answer questions get no partial credit.
- Result
- Immediate, with your score for each domain. It is kept in your account and does not appear on the certificate or the public profile.
- Voucher
- Each voucher is worth one attempt and is used when the certification exam is opened. A voucher bought on the site never expires. Whoever types the code takes the exam, so treat the code like a ticket.
- New attempt
- There is no waiting period and no limit. Each attempt uses a voucher, and questions are drawn again. If you do not pass, you get a 50% coupon for the same certification, valid for 90 days.
- Refund
- Within 14 days of purchase, if the voucher has not been used, through the same payment method.
- Technical problem
- Come back through the same address: the certification exam resumes with the same questions and the answers already saved. If a platform failure compromises your exam, a new attempt is released at no cost.
- Credential
- Issued when you pass, with a public verification code. It never expires and has no renewal or annual fee.
- Revocation
- A credential can be revoked for fraud, disclosure of questions, false identity, misleading use or administrative error. The code remains searchable and shows the revocation.
- Integrity
- The certification exam is individual and closed book, including artificial intelligence assistants. There is no camera, microphone or screen recording. Signals such as time per question and loss of window focus lead to human review, and no signal fails anyone on its own.
- Accessibility
- The certification exam screen works with keyboard and screen reader. Extended time of 25% or 50% is requested at checkout or in the account, in Certification exams, before using the voucher. For another adjustment, write to [email protected].
Where to study
The official guide indicates 48 hours of study, in paths of 8 weeks (appendix D of the guide).
Short on time? Study by weight: the domains below are in the order of how much they count in the certification exam.
- Analysis and interpretation of results (18%)
- Experiment design (16%)
- Threats to validity (16%)
- Metrics, instrumentation and unit of aggregation (14%)
- Sizing, sensitivity and duration (14%)
- Decision and experimentation programme (12%)
- Methods without full randomisation (10%)