A recent survey supports the idea that people who like strong flavor end up drinking more coffee. The only thing that worries the researcher is that she distributed the survey right before a holiday weekend, so she did not receive as many responses as she would have hoped.

Determine the confounding variable in the researcher's experiment.

• a.)
• The coffee temperature
• b.)
• The rate of coffee consumption
• c.)
• The people who like strong flavor
• d.)
• The holiday weekend