A coffee manufacturer is interested in whether the mean daily consumption of reg

Question

A coffee manufacturer is interested in whether the mean daily consumption of regular-coffee drinkers is less than that of decaffeinated-coffee drinkers. Assume the population standard deviation for those drinking regular coffee is 1.37 cups per day and 1.47 cups per day for those drinking decaffeinated coffee. A random sample of 47 regular-coffee drinkers showed a mean of 4.39 cups per day. A sample of 40 decaffeinated-coffee drinkers showed a mean of 5.78 cups per day.

The decision rule is to reject H0: r d if z < . (Negative amount should be indicated by a minus sign. Round your answer to 2 decimal places.)

The test statistic is z = . (Negative amount should be indicated by a minus sign. Round your answer to 2 decimal places.)

Explanation / Answer

1) one tailed test as one sided test is required

2)for 0.01 level rejection region RR Z<-2.33

3)for std error =(s12/n1+s22/n2)1/2=0.3065

hence test stat=(X1-X2)/std error =(4.39-5.78)/0.3065=-4.54

4) reject Ho

5) pvalue=0.000003

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