Question

It has been observed that electrical connectors manufactured by Jolt Electrical Supply Company last an average of 18.2 months and follow a normal distribution with a standard deviation of 1.7 months. Jolt agrees to replace any connector that fails within 19 months. Out of 500 connectors sold, how many does Jolt expect to replace, on average?

Answer 1

Answer:

Jolt can expect to replace 160 units.

Explanation:

given data:

standard deviation 1.7

average lfe of connectors = 18.2 months

number of connectors = 5000

$z(19) = \frac{(19-18.2)}{1.7}$

z(19)  = 0.4706

P(x< 19) = P(z< 0.4706)

P(x< 19) = 0.6810   from z table

therefore 68.1% fails within 19 months.

hence 0.3190   {100-68.1} will fail during that period.

number of unit of Jolt that need to be replace, on average is  0.319*500 = 160 units.