Question

According to Starbucks Coffee, a tall coffee is supposed to contain 12 fluid ounces. A consumer advocate decides to test the null hypothesis that there are 12 ounces in a tall coffee. She finds in a sample of 25 tall cups an average of 11.987 ounces of coffee, with a standard deviation of 0.032 ounces. Assume a significance level of 0.05 for the test.

1) What is the calculated value of the test statistic t? (round to three decimal places)

2) What is the NEGATIVE critical value of the test? (round to three decimal places)

3) What is the POSITIVE critical value of the test? (round to three decimal places)

4) Do we reject the null (yes or no)?

Question 11 options:

Answer 1

Ans. Hypothesis,

H0: there are 12 ounces in a tall coffee, against

H1: there are not 12 ounces of tall coffee (two tailed test)

i) t statistic = (11.987 - 12)/(0.032/25^0.5) = -2.03125

ii) t critical at 5% level of significance and 24 degrees of freedom (negative) = -2.0639

iii) t critical at 5% level of significance and 24 degrees of freedom (positive) = 2.0639

iv) As the t statistic lies between the negative and positive value of t critical, so, we fail to reject the null hypothesis. Hence, there are 12 ounces in a tall coffee.