A marketing company conducts a survey to examine people's interest in coffee and tea products. The company recruited a large random sample in the U.S. and asked each participant whether s/he liked coffee or tea better. They also recruited a large random sample in England and asked the participants the same question. Participants who did not like either coffee or tea were excluded from the survey study. To find out whether the coffee/tea preference differs significantly between the U.S. and England, the data should be analyzed _