Q30,paper 3, j 12. While unit testing a module, it is found that for a set of test data, maximum 90% of the code alone were tested with a probability of success 0.9. The reliability of the module is

Options (A) atleast greater than 0.9 (B) equal to 0.9 (C) atmost 0.81 (D) atleast 1/0.81
Ans © atmost 0.81
Software Reliability is the probability of failure-free software operation for a specified period of time in a specified environment. 90 % of the code has probability of success as .9. Let we have 2 blocks one is of 90% of unit and other is of 10%. Let first and second block both has .9 reliability then total reliability is .9*.9=.81. Since 2nd block will have reliability always less than .9 (given) hence total reliability will be (.9*(no less than .9) hence it will be atmost .81.