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 (millimeters). 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

First, we need to calculate the z-score:
z = (20.27 - 20.00) / 0.150 = 1.80

Using a z-table, we find that the area to the right of the z-score of 1.80 is 0.0359 or 3.59%. Therefore, 3.59% of the ball bearings will have diameters 20.27 mm or more.