A coffee-dispensing machine is supposed to deliver 12 ounces of liquid into a large paper cup, but the costumer believes that the actual amount is less. As a test he plans to obtain a sample of 30 cups of the dispensed liquid. The mean of his sample is 11.5 ounces. The machine operates with a known standard deviation of σ = 1.1 ounces. Is there enough evidence at the α = .05 level for him to claim the machine is broken?

Answer 1

Z = (mean-mean)/SEm

SEm = SD/sqrt n

Use table in back of text labeled area under normal distribution.

Answer 2

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