Software-Reliability
Question 1 |
The following table shoes the time between failures for a software system
The reliability of the system for one hour of operation assuming an exponential model is
0.45 | |
0.63 | |
0.84 | |
0.95 |
Question 1 Explanation:
MIBF = ∑(Start of downtime - Start of uptime)/No. of failures
MIBF = (6+4+8+5+6)/5 = 29/5
The probability or reliability that the product will work for a defined period of time without failure is given by
R(T) = exp(-T/MTBF); T = 1 hour
R(1) = e(-1/(29/5)) = e(-5/29) = 0.84
MIBF = (6+4+8+5+6)/5 = 29/5
The probability or reliability that the product will work for a defined period of time without failure is given by
R(T) = exp(-T/MTBF); T = 1 hour
R(1) = e(-1/(29/5)) = e(-5/29) = 0.84
Question 2 |
An Operating System (OS) crashes on the average once in 30 days, that is, the Mean Time Between Failures (MTBF) = 30 days. When this happens, it takes 10 minutes to recover the OS, that is, the Mean Time To Repair (MTTR) = 10 minutes. The availability of the OS with these reliability figures is approximately :
96.97% | |
97.97% | |
99.009% | |
99.97% |
Question 2 Explanation:
Given data,
-- Mean Time Between Failures (MTBF) = 30 days
-- Mean Time to Repairs (MTTR) = 10 minutes
-- Availability=?
Step-1: Given repair time in minutes, so we have to convert failure time in minutes.
30 days= 30 ∗ 24 ∗ 60 minutes
= 43,200 minutes
Step-2: Given options in percentages. We have to find availability in percentages.
Availability=(100-((10 / 43,200)∗100))%
= 100-0.023%
= 99.97%
-- Mean Time Between Failures (MTBF) = 30 days
-- Mean Time to Repairs (MTTR) = 10 minutes
-- Availability=?
Step-1: Given repair time in minutes, so we have to convert failure time in minutes.
30 days= 30 ∗ 24 ∗ 60 minutes
= 43,200 minutes
Step-2: Given options in percentages. We have to find availability in percentages.
Availability=(100-((10 / 43,200)∗100))%
= 100-0.023%
= 99.97%
Question 3 |
Software reliability is described with respect to
(A) Execution Time
(B) Calendar Time
(C) Clock Time
Choose the correct answer from the options given below:
(A) and (B) only | |
(B) and (C) only | |
(A), (B) and (C)
| |
(A) and (C) only |
Question 3 Explanation:
Software reliability testing is a field of software-testing that relates to testing a software's ability to function(which is related execution), given environmental conditions, for a particular amount of time(related to clock). Software reliability testing helps discover many problems in the software design and functionality.
Software reliability is also related to the ability of software to execute for a long period of time without any failure, which in turn related to calendar time.
Software reliability is also related to the ability of software to execute for a long period of time without any failure, which in turn related to calendar time.
There are 3 questions to complete.