A manager at a casual dining restaurant noted that 15% of customers ordered soda with their meal. In an effort to increase soda sales, the restaurant begins offering free refills with every soda order for a two-week trial period. During this trial period, 2100 customers were served and 357 of them ordered a soda.

The restaurant wants to know if offering free refills significantly increased the percentage of customers who bought sodas. This will be tested at a significance level of 0.05.

a) Find the sample proportion, p-hat.

b) Calculate the standard error. Is or used to calculate the standard error? Why?

c) Calculate the test-statistic (remember for proportions this is a z-score!) and the corresponding p-value. Round your test-statistic to 2 decimal places and your p-value to four decimal places.

d) Based on your p-value, what is the test decision (reject or do not reject the null hypothesis)?

e) Write out a conclusion for this hypothesis test in context based on your test decision.