CSP-11 CSP-11 D2.06 · Domain 2 · Program Management · 25%
FTA/ETA/Reliability Decision Lab
The stem gives an unwanted overpressure event and two failure probabilities. First decide whether you are reasoning backward from the top event or forward from an initiator. Then apply the correct AND/OR logic and challenge any claim of independence before using the number to support a design decision.
Updated . Independent CSP-11 practice. Not BCSP-endorsed. No pass guarantee.
Decision rule
Advanced FTA needs independent basic events and a defined top event.
A shared air header is one event wearing two labels.
In 20 seconds
- Advanced FTA needs independent basic events and a defined top event.
- FTA: TOP down through AND/OR to basic events.
- ETA: initiator through barrier success/failure.
- Independent AND of failures: multiply.
How to apply FTA/ETA/Reliability Decision Lab
THEORY: Cut sets show the smallest failing combinations. CALC: AND multiplies independent P. OR uses P(A)+P(B)-P(A)P(B) if independent. FIELD: Redraw after finding common air. ASSESS: Treating dependent events as AND 0.01 is the trap.
Worked case
Wrong first move: Multiply anyway. Correct move: Fix dependence; then quantify.
Why the rule holds
Related: 23, 113.
Same rule, different setting
A separator can reach an unmitigated overpressure only if the high-pressure trip fails and the relief function also fails on the same demand. Build the FTA logic, compute the independent-AND estimate, then challenge shared sensing, utilities, maintenance, and test practices before calling the layers independent.
A material hoist can overtravel if the upper-limit device fails and the backup stop does not act. Do not automatically treat an operator response as an independent redundant barrier when both responses may depend on the same visibility, alarm, power, or work conditions.
Picture / model
FTA: defined top event → Boolean AND/OR logic → basic events/cut sets. ETA: initiating event → barrier success/failure branches → consequences. Quantification is valid only for the stated probability basis and dependence assumptions.
Exam traps
Original SafePath contrasts for FTA/ETA/Reliability Decision Lab. These are study traps, not recalled BCSP items.
| Trap | Correct read |
|---|---|
| FTA | Deductive from TOP event |
| ETA | Inductive from initiator |
| AND gate | All inputs required |
| OR gate | Any input sufficient |
| MTBF | Mean — not a PEL or a skip ticket |
Field move
P(TOP) = 0.01 × 0.02 = 0.0002.
Scenarios
Scenario 1 · Applied Scenario · CSP-11 D2.06
P(A)=0.01, P(B)=0.02, independent, both required to cause the TOP. P(TOP)?
Best action: 0.0002
Why: Both independent events are required, so the top probability is the product 0.01 × 0.02 = 0.0002. Adding them gives 0.03.
Scenario 2 · Fundamental · CSP-11 D2.06
How can overpressure occur from combinations of faults. Best tool?
Best action: Fault tree from the TOP event.
Why: Evaluate the best response. Failure modes, five-why, and barrier questions answer different problems. A five-why that ends in complacency misses a missing engineered barrier. Design that removes the initiator beats a laminated tree. Mean time between failures is not a reason to skip inspection. Thi…
Scenario 3 · Applied Scenario · CSP-11 D2.06
Independent series components with R=0.9 and R=0.9. System reliability?
Best action: 0.81
Why: Independent units in series multiply: 0.9 × 0.9 = 0.81. The parallel-style figure 0.99, the sum 1.80, and one unit's 0.9 are different results.
If the stem says this
| Stem signal | Best direction |
|---|---|
| how can TOP occur | FTA |
| given initiator, barrier success/fail | ETA |
| independent AND of rare failures | multiply |
| shared power or shared tap | do not assume independence |
| tree is pretty but a second trip is open | add the independent layer |
| two answers work | higher hierarchy / system / design |
Check before you leave
- ✓ FTA: TOP down through AND/OR to basic events.
- ✓ ETA: initiator through barrier success/failure.
- ✓ Independent AND of failures: multiply.
- ✓ Series reliability: multiply success probabilities.
- ✓ Common-cause kills naive products.
- ✓ MTBF is not permission to skip design.
Blueprint mapping
FTA/ETA/Reliability Decision Lab is the SafePath study class for CSP-11 D2.06 inside CSP-11 Domain 2, Program Management (25%). A high-weight management domain focused on measuring performance, investigating incidents, managing change, building systems, leading people, controlling records and resources, and interpreting data.
SafePath uses the publicly posted CSP-11 outline as a study map. It does not reproduce official exam content, and it is not affiliated with or endorsed by BCSP or Pearson VUE.
Practice / flashcards / formulas
More classes in Program Management
Nearby lessons mapped to the same CSP-11 domain.
CSP-11 D2.06
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Guides that use FTA/ETA/Reliability Decision Lab
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- CSP-11 exam prep guideDomain weights, sample items, and a study sequence
- CSP-11 blueprint and weightsSeven published domains and the class map
- Seven-domain study directoryScope, tasks, and links into each lesson
FTA/ETA/Reliability Decision Lab study questions
- What decision does the FTA/ETA/Reliability Decision Lab class train?
- Advanced FTA needs independent basic events and a defined top event. This is independent SafePath CSP practice for CSP-11 D2.06. It is not an official BCSP item and it is not a pass guarantee.
- What exam trap shows up in FTA/ETA/Reliability Decision Lab?
- A common miss treats this as sufficient: FTA The stronger read is: Deductive from TOP event
- How does FTA/ETA/Reliability Decision Lab map to the CSP-11 blueprint?
- SafePath maps this class to CSP-11 D2.06 in Domain 2, Program Management (25% of the published blueprint). Use the public outline for study planning. SafePath is not affiliated with or endorsed by BCSP.
Verify
Verify: Confirm current certification requirements with BCSP and technical requirements with the cited authoritative standard.