Question

The breakdown voltage of a certain type of diode has a mean 39.8 V and standard deviation 0.72 V. If 81 diodes are randomly selected, what is the probability that the average breakdown voltage exceeds 40 V?

Answer 1

Solution :

Given that ,

mean = = 39.8

standard deviation = = 0.72

= / n = 0.72 / 81 = 0.08

P( > 40) = 1 - P( < 40)

= 1 - P[( - ) / < (40- 39.8) / 0.08]

= 1 - P(z < 2.5)

= 1 - 0.9938

= 0.0062

Probability = 0.0062