Ball-Bearings, Inc. produces ball bearings automatically on a Kronar BBX machine. For one of the ball bearings, the mean diameter is set at 20.00 mm (millimetres). The standard deviation of the production over a long period of time was computed to be 0.150 mm. What percent of the ball bearings will have diameters 20.27 mm or more?
A) 41.00%
B) 12.62%
C) 3.59%
D) 85.00%

Question

Quizplus · Accepted Answer

We need to find the probability of getting a ball bearing with a diameter of 20.27 mm or more. This can be calculated using the z-score formula as follows:

z = (X - μ) / σ

where X is the diameter we want to find the probability for, μ is the mean diameter, and σ is the standard deviation.

z = (20.27 - 20) / 0.15
z = 1.80

Looking up the z-value in a standard normal distribution table or using a calculator, we find that the probability of getting a z-value of 1.80 or greater is 0.0359 or 3.59%.

Therefore, the answer is choice C.