Question

Assume that process that makes the parts can be altered to adjust the overall mean of the reflectiveness score. Also assume that if an individual part has a score less than 85, then the part is given a passing quality score. The adjusted value of the true mean in population S that would result in approximately 80% of parts from that population being given a passing score is:______
a. greater than 80
b. less than 80
c. equal to 80

Answer 1

Answer:

c. equal to 80

Step-by-step explanation:

Given that:

The population mean = 80

The standard deviation is = 6

The sample mean = 85

The objective is to find the probability that is less than 85

$P(X < 85) = P( Z < \dfrac{x-\mu}{\sigma})$

$P(X < 85) = P( Z < \dfrac{85-80}{6})$

$P(X < 85) = P( Z < \dfrac{5}{6})$

$P(X < 85) = P( Z < 0.833)$

From the standard normal table

P(X <85) = 0.7977

P(X< 85) = 79.77%

P(X< 85) = 80%

Therefore, The adjusted value of the true mean in population S that would result in approximately 80% of parts from that population being given a passing score is:  equal to 80    .