The American Water Works Association estimates that the average person in the United States uses 123 gallons of water per day. Suppose some researchers believe that more water is being used now and want to test to determine whether this is so. They randomly select a sample of Americans and carefully keep track of the water used by each sample member for a day, then analyze the results by using a statistical computer software package. The output is given here. Assume ± = .05. How many people were sampled? What was the sample mean? Was this a one- or two-tailed test? What was the result of the study? What decision could be stated about the null hypothesis from these results?

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One-Sample Z: C1 Test of mu-123 vs > 123 The assumed standard deviation27.68 N Mean SE Mean 95% Lower Bound 40 132.360 4.38 (123.78) 2.14 0.016