Question

According to the Coffee Research Organization, the typical American coffee drinker consumes an average of 3.2 cups per day. A sample of 10 senior citizens revealed they consumed the following amounts, reported in cups, of coffee yesterday.

2        2         3         3         3        4          4          3         3           3

At the 0.01 significance level, can we conclude that the average American consumes less that 3.2 cups per day?

Question: What are the hypotheses and the complete Decision Rule?

Answer 1

We want to know whether the average American consumes less than 3.2 cups. We use a one tailed (left tailed Hypothesis.

H0: = 3.2

Ha: < 3.2

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Since n, the number of observations is less than 30 and population standard deviation is unknown, we use the students t test.

At = 0.01, df = n - 1 = 9 the critical value is 3.25

The Decision rule

By the critical value method: If t test is < -3.25, reject H0

By the p value method: If the p value is < (0.01), Reject H0.

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