An instrument consists of two units. Each unit must function for the instrument to operate. The reliability of the first unit is 0.9 that of the second unit is 0.8. The instrument is tested fails. The probability that "only the first unit failed the second unit is sound" is :

Question

An instrument consists of two units. Each unit must function for the instrument to operate. The reliability of the first unit is 0.9 that of the second unit is 0.8. The instrument is tested fails. The probability that "only the first unit failed the second unit is sound" is : (A) 1/7 (B) 2/7 (C) 3/7 (D) 4/7

Tardigrade Admin · Accepted Answer

A: the instrument has failed B1: first unit fails and second is healthy B 2: first unit healthy and second unit fails B 3: both fails B 4: both healthy

Q. An instrument consists of two units. Each unit must function for the instrument to operate. The reliability of the first unit is 0.9 & that of the second unit is 0.8. The instrument is tested & fails. The probability that "only the first unit failed & the second unit is sound" is :

1/7

2/7

3/7

4/7

A: the instrument has failed
$B_{1}$ : first unit fails and second is healthy
$B_{2}$ : first unit healthy and second unit fails
$B_{3}$ : both fails
$B_{4}$ : both healthy

Q. An instrument consists of two units. Each unit must function for the instrument to operate. The reliability of the first unit is 0.9 & that of the second unit is 0.8. The instrument is tested & fails. The probability that "only the first unit failed & the second unit is sound" is :

1/7

2/7

3/7

4/7

A: the instrument has failed B1​ : first unit fails and second is healthy B2​ : first unit healthy and second unit fails B3​ : both fails B4​ : both healthy

A: the instrument has failed
$B_{1}$ : first unit fails and second is healthy
$B_{2}$ : first unit healthy and second unit fails
$B_{3}$ : both fails
$B_{4}$ : both healthy