Question

Due to the increase in the consumption of bottled water vs. tap water in North America, researchers conducted a study to determine if there are differences in some of the mineral content of these two types of drinking water, focusing in particular to the amount of calcium present between the two types. In a random sample of 36 cities, it was found the average calcium concentration was 34 mg/L with a standard deviation of 21 mg/L for tap water (T). A random sample of 28 commercially available bottled waters (B) was taken and the average calcium concentration was 18 mg/L with a standard deviation of 22 mg/L. Does the data provide evidence that tap water has higher calcium concentration than bottled water? Test at 5% level of significance.

The value of the appropriate test statistic is ______.

Question 1 options:

A)

Z = 2.94

B)

t = 2.94

C)

Z = 13.67

D)

t = 13.67

E)

Z = 11.69

Answer 1