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 1.21 cups per day and 1.40 cups per day for those drinking decaffeinated coffee. A random sample of 54 regular-coffee drinkers showed a mean of 4.59 cups per day. A sample of 49 decaffeinated-coffee drinkers showed a mean of 5.64 cups per day. Use the 10 significance level. 1. This is a tailed test. 2. The decision rule is to reject H_0: m_r greaterthanorequalto mu_d if z

Explanation / Answer

The statistical software output for this problem is:

Two sample Z summary hypothesis test:
1 : Mean of population 1 (Std. dev. = 1.21)
2 : Mean of population 2 (Std. dev. = 1.4)
1 - 2 : Difference between two means
H0 : 1 - 2 = 0
HA : 1 - 2 < 0

Hypothesis test results:

Hence,

1. Left - tailed test or One tailed test (Both are correct; its just that it will depend on the dropdown options you have)

2. z < -1.28

3. z = -3.97

4. Reject Ho

5. The p - value is 0.0000

Difference n1 n2 Sample mean Std. err. Z-stat P-value 1 - 2 49 49 -1.05 0.26434748 -3.9720446 <0.0001

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