Try a one-sample z-test.
Hypotheses:
Ho: µ = 24.2 -->null hypothesis
Ha: µ does not equal 24.2 -->alternate hypothesis
Check the cutoff or critical value to reject the null using a z-table at 0.05 level for a two-tailed test. If the test statistic calculated exceeds either the positive or negative critical value from the table, reject the null and conclude a difference. If the test statistic does not exceed the critical value from the table, do not reject the null.
Use 23.5 as the sample mean.
Use 3.2 for standard deviation.
Use 120 for sample size.
I hope this will help get you started.
The U.S. Department of Agriculture claims that the mean consumption of coffee by the person in the United States is 24.2 gallons per year. A random sample of 120 people in the United States shows that the mean coffee consumption is 23.5 gallons per year with a standard deviation of 3.2 gallons. At a=0.05, can you reject the claim?
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