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ISTQB CTAL-TTA Exam - Topic 4 Question 53 Discussion

Posted by Julianna on Jun 30, 2026 at 10:35 PM

The stakeholders in a new system want its mean time between failure to be three months or longer, with a mean time to repair the system of ten minutes or less when it does fail. When planning and specifying reliability tests to be performed before release, which ONE of the following is a factor that must be considered?

Suggested Answer: B

Analysis:

For a system to meet its reliability requirements, it must maintain a mean time between failure (MTBF) of three months or longer and a mean time to repair (MTTR) of ten minutes or less. When planning and specifying reliability tests, several factors must be considered to ensure these requirements are met.

Key Factor:

B . Determining the target availability for the system:

Availability is a critical factor that encompasses both the MTBF and MTTR. Availability is calculated based on the uptime and downtime of the system, which directly correlates with MTBF and MTTR. Determining the target availability helps ensure that the system can meet the required reliability standards by specifying acceptable levels of uptime and downtime.

Explanation of Incorrect Options:

A . Defining the replaceability requirements:

Replaceability pertains to the ease with which components can be replaced or updated. While important for maintainability, it is not the primary focus for reliability testing in this context.

C . Monitoring reliability in production:

Monitoring in production is important for ongoing reliability assessment but is not a primary consideration when planning and specifying tests before release.

D . Configuring a production-like test environment:

This is essential for accurate testing but is a logistical consideration rather than a direct factor in the reliability requirements.


The ISTQB CTAL-TTA syllabus and standard practices in reliability testing emphasize the importance of availability metrics in planning reliability tests.

Sources:

ISTQB-CTAL-TTA Syllabus

General knowledge on reliability testing and availability.

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21 comments · newest first
CR
Craig 2 days ago
D makes sense. A test environment should mimic production.
LI
Lizette 7 days ago
C is key too. Monitoring helps improve reliability over time.
TR
Trinidad 12 days ago
I agree, but A is also important. Replaceability can affect downtime.
CU
Curt 17 days ago
I think B is crucial. Target availability impacts everything.
DE
Deandrea 23 days ago
Exactly! Each plays a role in overall system performance.
LU
Ludivina 28 days ago
So, we need to balance all these factors for a reliable system.
KR
Kris 1 month ago
Right, but we need a solid test environment first. D is essential.
HO
Hollis 1 month ago
C is key too. Monitoring in production shows real-world reliability.
DE
Deandrea 1 month ago
True, but if we don't know the availability, we can't plan repairs.
LA
Lai 2 months ago
But A is also important. Replaceability affects downtime.
KR
Kris 2 months ago
Agreed! If we don't set that, how can we measure success?
LU
Ludivina 2 months ago
I think B is crucial. Target availability impacts everything.
BE
Belen 2 months ago
C sounds interesting, but is it really necessary before release?
AL
Alpha 2 months ago
Totally agree with B, target availability is key!
MY
Myrtie 2 months ago
Wait, ten minutes to repair? That seems too optimistic.
FR
France 3 months ago
I think A is crucial too, can't just ignore replaceability!
VA
Val 3 months ago
B is definitely the most important factor here.
ER
Ernie 3 months ago
I keep mixing up the replaceability requirements and the target availability. I guess both are important, but which one is more critical here?
KE
Keneth 3 months ago
I feel like configuring a production-like test environment could be key, especially since we want to simulate real-world conditions.
RA
Rashida 3 months ago
I'm not entirely sure, but I remember something about monitoring reliability in production being important for long-term performance.
VI
Vi 4 months ago
I think we might need to focus on the target availability for the system. It seems crucial for meeting those reliability goals.
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