Question

BearCo produces alutin (and alloy of aluminium and tin) bearings for truck engines. Prior to shaping, ingots of alutin pass through a rolling mill, where they are reduced to a mean thickness of 3.05 mm , with a standard deviation of 0.025 mm. The alutin ingots can be shaped if their thickness is between 2.97 mm and 3.08 mm. These ingots are described as in spec. If they are outside that range they are out of spec and need to be melted down and recast.

a) Assuming that alutin ingot thickness follows a normal distribution, determine the probability that a randomly selected ingot is ”in spec”.

Answer 1

so we want

Answer 2

P( 2.97 < X < 3.08) , where X ~ N (3.05, .025)