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 20 tall cups an average of 11.99 ounces of coffee, with a standard deviation of .01 ounces. From the above information, what would positive critical value for t in a two-tailed test at a significance level of .01? (refer to the provided t table).

Your Answer:

Answer 1

Given, sample size = n = 20

population mean = μ = 12

smaple mean = x̅ = 11.99

sample standard deviation = s = 0.01

The hypothesis is given by:

H₀: μ = 12 against

H₁: μ ≠ 12

The test statistic is given by:

t = (x̅ - μ)/(s/√n)

t = (11.99-12)/(0.01/√20)

t = -4.472

|t| = 4.472

The critical value (table value) is:

t_crit = t_0.005,20-1 = 2.861